Systems and methods for hierarchical global load balancing

ABSTRACT

Systems and methods are disclosed for providing a hierarchy of appliances to access resources across branch offices. A method comprises: establishing, by a first aggregator appliance, connections with a first plurality of branch office appliances; establishing, by a second aggregator appliance, connections with a second plurality of branch office appliances, the first plurality not having information identifying the second plurality; receiving, by the first aggregator appliance, from a first branch office appliance a request from a client for access to a resource; identifying, by the first aggregator appliance via the second aggregator appliance, a second branch office appliance from the second plurality to service the request; transmitting, by the first aggregator appliance, to the first branch office appliance information identifying the second branch office appliance; and establishing, by the first branch office appliance, a connection with the second branch office appliance. Corresponding systems are also described.

FIELD OF THE INVENTION

The present invention generally relates to data communication networks.In particular, the present invention relates to systems and methods forproviding aggregator appliances for global and hierarchical loadbalancing of branch offices.

BACKGROUND OF THE INVENTION

A corporate or enterprise network may service many branch offices. Eachbranch office may have its own network, servers and resources. Anappliance may be deployed at a branch office to provide gateway serviceslocally to the client or servers located at the branch office. In thecorporate-wide network, branch office appliances may be deployed at eachof the branch offices. Many resources, such as servers, applications,data files may be deployed across these branch offices. Additionally, abranch office may have under utilized resources and available computingtime.

At any of the branch offices there may be resources that could beavailable or useful to access by users or computing devices at otherbranch offices. For example, a client of a first branch office may wantto access a resource, such as an application, on a server at a secondbranch office. In some cases, the client of the first branch office isnot aware of the existence or availability of resources at the secondbranch office. In other cases, resources at branch offices lay idle asthey are not easily available to users across the corporate network.This results in inefficient use of the corporate network and deployedresource. In order to avail a client of a branch office access toresources from another branch office, an administrator may need tomanually and specifically configure the gateway or branch officeappliance to know of the other appliances in the network. With resourcesdeployed across many branch offices, each of the branch officeappliances may need to be manually configured to know of the otherbranch office appliances. This leads to significant amount of time andcosts in configuring and maintaining multiple branch office appliancesor gateway.

It would, therefore, be desirable to provide systems and methods toreduce branch office configuration while load-balancing resourcesglobally across the enterprise and branch offices.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed towards an aggregator appliance thatprovides aggregation and load-balancing of branch office appliances in ahierarchical fashion and a manner that reduces configuration of thebranch office appliance. Any of the branch office appliances may beconfigured to know of or identify a single aggregator appliance 400. Forexample, a first branch office appliance may be configured to identifyand connect to the first aggregator appliance. The first branch officeappliance may not be configured to have any information and thereforemay not know of the second aggregator appliance or any branch officeappliances connected to the second aggregator appliance. In this manner,the configuration of branch office appliance is reduced. Even though theconfiguration is reduced, a branch office appliance servicing a requestmay access any of the other appliances known to an aggregator appliance.Since the aggregator appliances share information on branch officeappliance, a first aggregator appliance can identify to a first branchoffice appliance information identifying any of the branch officeappliances connected via any of the aggregator appliances. In this way,resource requests can be load balanced globally across all branchoffices and branch office appliances.

In one aspect, the present invention is related to a method forproviding a hierarchy of appliances to more efficiently access resourcesacross a plurality of branch offices. The method includes the steps of:establishing, by a first aggregator appliance, connections with a firstplurality of branch office appliances, and establishing, by a secondaggregator appliance, connections with a second plurality of branchoffice appliances. The first plurality of branch office appliances maynot have information identifying the second plurality of branch officeappliances. The second plurality of branch office appliances may alsonot have information identifying the first plurality of branch officeappliances. The method includes receiving, by the first aggregatorappliance, from a first branch office appliance of the first pluralityof branch office a request from a client for access to a resource. Thefirst aggregator appliance identifies via the second aggregatorappliance a second branch office appliance from the second plurality ofbranch office appliances to service the request. The first aggregatorappliance transmits to one of the client or a first branch officeappliance information identifying the second branch office appliance.The method includes the client establishing a connection with the secondbranch office appliance.

In one embodiment, the method includes transmitting, by the first branchoffice appliance, information identifying the second branch officeappliance to the client. In another embodiment, the method includesestablishes, by the client via the first branch office appliance, asecond connection via the second branch office appliance with a server.In some embodiments, the method includes establishing, by the firstaggregator appliance, communications with the second aggregatorappliance. In one embodiment, the first aggregator appliancecommunicates information about the first plurality of branch officeappliances to the second aggregator appliance. In another embodiments,the second aggregator appliance communicates information about thesecond plurality of branch office appliances to the first aggregatorappliance.

In another embodiment, the method includes determining, by the firstaggregator appliance, information on performance or operationalcharacteristics for each of the first plurality of branch officeappliances. In some embodiments, the method includes determining, by thesecond aggregator appliance, performance or operational characteristicsof each of the second plurality of branch office appliances. In oneembodiment, the method includes selecting, by the first or secondaggregator appliance, the second branch office appliance based on one ofthe performance or operational characteristics.

In yet another embodiment, the method includes by the first officebranch office appliance or the second branch office appliance,communications between the client and the server. The method may includeaccelerating using one or more of the following techniques: 1)compression, 2) TCP connection pooling, 3) TCP connection multiplexing,4) TCP buffering, and 5) caching. In some embodiments, the firstaggregator appliance or the second aggregator appliance is deployed at adata center. In another embodiment, the client is deployed at the firstbranch office.

In another aspect, the present invention is related to a system forproviding a hierarchy of appliances to more efficiently access resourcesacross a plurality of branch offices, the system comprises a firstaggregator appliance and a second aggregator appliance. The firstaggregator appliance establishes connections with a first plurality ofbranch office appliances. The second aggregator appliance establishesconnections with a second plurality of branch office appliances. Thefirst plurality of branch office appliances may not have informationidentifying the second plurality of branch office appliances. The secondplurality of branch office appliances may also not have informationidentifying the first plurality of branch office appliances. The systemalso includes a first branch office appliance of the first plurality ofbranch offices transmitting to the first aggregator appliance a requestfrom a client for access to a resource. The first aggregator applianceidentifies via the second aggregator appliance a second branch officeappliance from the second plurality of branch office appliances toservice the request and transmits to the first branch office applianceinformation identifying the second branch office appliance. The systemalso includes the client establishing a connection with the secondbranch office appliance.

In one embodiment, the first branch office appliance transmitsinformation identifying the second branch office appliance to theclient. In another embodiment, the client establishes via the firstbranch office appliance a second connection via the second branch officeappliance with a server. In some embodiments, the first aggregatorappliance establishes communications with the second aggregatorappliance. In one embodiment, the first aggregator appliancecommunicates information about the first plurality of branch officeappliances to the second aggregator appliance. In yet anotherembodiment, the second aggregator appliance communicates informationabout the second plurality of branch office appliances to the firstaggregator appliance. In some embodiments, the first or secondaggregator appliance determines information on performance oroperational charactersitics for each of the first plurality of branchoffice appliances. In another embodiment of the system, the firstaggregator appliance selects the second branch office appliance based onone of the performance or operational characteristics.

In some embodiments, the first office branch office appliance or thesecond branch office appliance accelerates communications between theclient and a server. The acceleration techniques may include one or moreof the following: 1) compression, 2) TCP connection pooling, 3) TCPconnection multiplexing, 4) TCP buffering, and 5) caching. In otherembodiments, the first aggregator appliance or the second aggregatorappliance is deployed at a data center. In one embodiment, the client isdeployed at the first branch office.

The details of various embodiments of the invention are set forth in theaccompanying drawings and the description below.

BRIEF DESCRIPTION OF THE FIGURES

The foregoing and other objects, aspects, features, and advantages ofthe invention will become more apparent and better understood byreferring to the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1A is a block diagram of an embodiment of a network environment fora client to access a server via an appliance;

FIG. 1B is a block diagram of an embodiment of an environment fordelivering a computing environment from a server to a client via anappliance;

FIGS. 1C and 1D are block diagrams of embodiments of a computing device;

FIG. 2A is a block diagram of an embodiment of an appliance forprocessing communications between a client and a server;

FIG. 2B is a block diagram of another embodiment of an appliance foroptimizing, accelerating, load-balancing and routing communicationsbetween a client and a server;

FIG. 3 is a block diagram of an embodiment of a client for communicatingwith a server via the appliance;

FIG. 4A is a block diagram of an embodiment of aggregator appliances toaccess resources across branch offices;

FIG. 4B is a block diagram of another embodiment of a deployment ofaggregator appliances to load balance a plurality of branch offices; and

FIG. 5 is a flow diagram of steps of an embodiment of a method forpracticing hierarchical load balancing with aggregator appliances toaccess resources across branch offices.

The features and advantages of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements.

DETAILED DESCRIPTION OF THE INVENTION

A. Network and Computing Environment

Prior to discussing the specifics of embodiments of the systems andmethods of an appliance and/or client, it may be helpful to discuss thenetwork and computing environments in which such embodiments may bedeployed. Referring now to FIG. 1A, an embodiment of a networkenvironment is depicted. In brief overview, the network environmentcomprises one or more clients 102 a-102 n (also generally referred to aslocal machine(s) 102, or client(s) 102) in communication with one ormore servers 106 a-106 n (also generally referred to as server(s) 106,or remote machine(s) 106) via one or more networks 104, 104′ (generallyreferred to as network 104). In some embodiments, a client 102communicates with a server 106 via an appliance 200.

Although FIG. 1A shows a network 104 and a network 104′ between theclients 102 and the servers 106, the clients 102 and the servers 106 maybe on the same network 104. The networks 104 and 104′ can be the sametype of network or different types of networks. The network 104 and/orthe network 104′ can be a local-area network (LAN), such as a companyIntranet, a metropolitan area network (MAN), or a wide area network(WAN), such as the Internet or the World Wide Web. In one embodiment,network 104′ may be a private network and network 104 may be a publicnetwork. In some embodiments, network 104 may be a private network andnetwork 104′ a public network. In another embodiment, networks 104 and104′ may both be private networks. In some embodiments, clients 102 maybe located at a branch office of a corporate enterprise communicatingvia a WAN connection over the network 104 to the servers 106 located ata corporate data center.

The network 104 and/or 104′ be any type and/or form of network and mayinclude any of the following: a point to point network, a broadcastnetwork, a wide area network, a local area network, a telecommunicationsnetwork, a data communication network, a computer network, an ATM(Asynchronous Transfer Mode) network, a SONET (Synchronous OpticalNetwork) network, a SDH (Synchronous Digital Hierarchy) network, awireless network and a wireline network. In some embodiments, thenetwork 104 may comprise a wireless link, such as an infrared channel orsatellite band. The topology of the network 104 and/or 104′ may be abus, star, or ring network topology. The network 104 and/or 104′ andnetwork topology may be of any such network or network topology as knownto those ordinarily skilled in the art capable of supporting theoperations described herein.

As shown in FIG. 1A, the appliance 200, which also may be referred to asan interface unit 200 or gateway 200, is shown between the networks 104and 104′. In some embodiments, the appliance 200 may be located onnetwork 104. For example, a branch office of a corporate enterprise maydeploy an appliance 200 at the branch office. In other embodiments, theappliance 200 may be located on network 104′. For example, an appliance200 may be located at a corporate data center. In yet anotherembodiment, a plurality of appliances 200 may be deployed on network104. In some embodiments, a plurality of appliances 200 may be deployedon network 104′. In one embodiment, a first appliance 200 communicateswith a second appliance 200′. In other embodiments, the appliance 200could be a part of any client 102 or server 106 on the same or differentnetwork 104,104′ as the client 102. One or more appliances 200 may belocated at any point in the network or network communications pathbetween a client 102 and a server 106.

In one embodiment, the system may include multiple, logically-groupedservers 106. In these embodiments, the logical group of servers may bereferred to as a server farm 38. In some of these embodiments, theserves 106 may be geographically dispersed. In some cases, a farm 38 maybe administered as a single entity. In other embodiments, the serverfarm 38 comprises a plurality of server farms 38. In one embodiment, theserver farm executes one or more applications on behalf of one or moreclients 102.

The servers 106 within each farm 38 can be heterogeneous. One or more ofthe servers 106 can operate according to one type of operating systemplatform (e.g., WINDOWS NT, manufactured by Microsoft Corp. of Redmond,Wash.), while one or more of the other servers 106 can operate onaccording to another type of operating system platform (e.g., Unix orLinux). The servers 106 of each farm 38 do not need to be physicallyproximate to another server 106 in the same farm 38. Thus, the group ofservers 106 logically grouped as a farm 38 may be interconnected using awide-area network (WAN) connection or medium-area network (MAN)connection. For example, a farm 38 may include servers 106 physicallylocated in different continents or different regions of a continent,country, state, city, campus, or room. Data transmission speeds betweenservers 106 in the farm 38 can be increased if the servers 106 areconnected using a local-area network (LAN) connection or some form ofdirect connection.

Servers 106 may be referred to as a file server, application server, webserver, proxy server, or gateway server. In some embodiments, a server106 may have the capacity to function as either an application server oras a master application server. In one embodiment, a server 106 mayinclude an Active Directory. The clients 102 may also be referred to asclient nodes or endpoints. In some embodiments, a client 102 has thecapacity to function as both a client node seeking access toapplications on a server and as an application server providing accessto hosted applications for other clients 102 a-102 n.

In some embodiments, a client 102 communicates with a server 106. In oneembodiment, the client 102 communicates directly with one of the servers106 in a farm 38. In another embodiment, the client 102 executes aprogram neighborhood application to communicate with a server 106 in afarm 38. In still another embodiment, the server 106 provides thefunctionality of a master node. In some embodiments, the client 102communicates with the server 106 in the farm 38 through a network 104.Over the network 104, the client 102 can, for example, request executionof various applications hosted by the servers 106 a-106 n in the farm 38and receive output of the results of the application execution fordisplay. In some embodiments, only the master node provides thefunctionality required to identify and provide address informationassociated with a server 106′ hosting a requested application.

In one embodiment, the server 106 provides functionality of a webserver. In another embodiment, the server 106 a receives requests fromthe client 102, forwards the requests to a second server 106 b andresponds to the request by the client 102 with a response to the requestfrom the server 106 b. In still another embodiment, the server 106acquires an enumeration of applications available to the client 102 andaddress information associated with a server 106 hosting an applicationidentified by the enumeration of applications. In yet anotherembodiment, the server 106 presents the response to the request to theclient 102 using a web interface. In one embodiment, the client 102communicates directly with the server 106 to access the identifiedapplication. In another embodiment, the client 102 receives applicationoutput data, such as display data, generated by an execution of theidentified application on the server 106.

Referring now to FIG. 1B, a network environment for delivering and/oroperating a computing environment on a client 102 is depicted. In someembodiments, a server 106 includes an application delivery system 190for delivering a computing environment or an application and/or datafile to one or more clients 102. In brief overview, a client 10 is incommunication with a server 106 via network 104, 104′ and appliance 200.For example, the client 102 may reside in a remote office of a company,e.g., a branch office, and the server 106 may reside at a corporate datacenter. The client 102 comprises a client agent 120, and a computingenvironment 15. The computing environment 15 may execute or operate anapplication that accesses, processes or uses a data file. The computingenvironment 15, application and/or data file may be delivered via theappliance 200 and/or the server 106.

In some embodiments, the appliance 200 accelerates delivery of acomputing environment 15, or any portion thereof, to a client 102. Inone embodiment, the appliance 200 accelerates the delivery of thecomputing environment 15 by the application delivery system 190. Forexample, the embodiments described herein may be used to acceleratedelivery of a streaming application and data file processable by theapplication from a central corporate data center to a remote userlocation, such as a branch office of the company. In another embodiment,the appliance 200 accelerates transport layer traffic between a client102 and a server 106. The appliance 200 may provide accelerationtechniques for accelerating any transport layer payload from a server106 to a client 102, such as: 1) transport layer connection pooling, 2)transport layer connection multiplexing, 3) transport control protocolbuffering, 4) compression and 5) caching. In some embodiments, theappliance 200 provides load balancing of servers 106 in responding torequests from clients 102. In other embodiments, the appliance 200 actsas a proxy or access server to provide access to the one or more servers106. In another embodiment, the appliance 200 provides a secure virtualprivate network connection from a first network 104 of the client 102 tothe second network 104′ of the server 106, such as an SSL VPNconnection. It yet other embodiments, the appliance 200 providesapplication firewall security, control and management of the connectionand communications between a client 102 and a server 106.

In some embodiments, the application delivery management system 190provides application delivery techniques to deliver a computingenvironment to a desktop of a user, remote or otherwise, based on aplurality of execution methods and based on any authentication andauthorization policies applied via a policy engine 195. With thesetechniques, a remote user may obtain a computing environment and accessto server stored applications and data files from any network connecteddevice 100. In one embodiment, the application delivery system 190 mayreside or execute on a server 106. In another embodiment, theapplication delivery system 190 may reside or execute on a plurality ofservers 106 a-106 n. In some embodiments, the application deliverysystem 190 may execute in a server farm 38. In one embodiment, theserver 106 executing the application delivery system 190 may also storeor provide the application and data file. In another embodiment, a firstset of one or more servers 106 may execute the application deliverysystem 190, and a different server 106 n may store or provide theapplication and data file. In some embodiments, each of the applicationdelivery system 190, the application, and data file may reside or belocated on different servers. In yet another embodiment, any portion ofthe application delivery system 190 may reside, execute or be stored onor distributed to the appliance 200, or a plurality of appliances.

The client 102 may include a computing environment 15 for executing anapplication that uses or processes a data file. The client 102 vianetworks 104, 104′ and appliance 200 may request an application and datafile from the server 106. In one embodiment, the appliance 200 mayforward a request from the client 102 to the server 106. For example,the client 102 may not have the application and data file stored oraccessible locally. In response to the request, the application deliverysystem 190 and/or server 106 may deliver the application and data fileto the client 102. For example, in one embodiment, the server 106 maytransmit the application as an application stream to operate incomputing environment 15 on client 102.

In some embodiments, the application delivery system 190 comprises anyportion of the Citrix Access Suite™ by Citrix Systems, Inc., such as theMetaFrame or Citrix Presentation Server™ and/or any of the Microsoft®Windows Terminal Services manufactured by the Microsoft Corporation. Inone embodiment, the application delivery system 190 may deliver one ormore applications to clients 102 or users via a remote-display protocolor otherwise via remote-based or server-based computing. In anotherembodiment, the application delivery system 190 may deliver one or moreapplications to clients or users via steaming of the application.

In one embodiment, the application delivery system 190 includes a policyengine 195 for controlling and managing the access to, selection ofapplication execution methods and the delivery of applications. In someembodiments, the policy engine 195 determines the one or moreapplications a user or client 102 may access. In another embodiment, thepolicy engine 195 determines how the application should be delivered tothe user or client 102, e.g., the method of execution. In someembodiments, the application delivery system 190 provides a plurality ofdelivery techniques from which to select a method of applicationexecution, such as a server-based computing, streaming or delivering theapplication locally to the client 120 for local execution.

In one embodiment, a client 102 requests execution of an applicationprogram and the application delivery system 190 comprising a server 106selects a method of executing the application program. In someembodiments, the server 106 receives credentials from the client 102. Inanother embodiment, the server 106 receives a request for an enumerationof available applications from the client 102. In one embodiment, inresponse to the request or receipt of credentials, the applicationdelivery system 190 enumerates a plurality of application programsavailable to the client 102. The application delivery system 190receives a request to execute an enumerated application. The applicationdelivery system 190 selects one of a predetermined number of methods forexecuting the enumerated application, for example, responsive to apolicy of a policy engine. The application delivery system 190 mayselect a method of execution of the application enabling the client 102to receive application-output data generated by execution of theapplication program on a server 106. The application delivery system 190may select a method of execution of the application enabling the localmachine 10 to execute the application program locally after retrieving aplurality of application files comprising the application. In yetanother embodiment, the application delivery system 190 may select amethod of execution of the application to stream the application via thenetwork 104 to the client 102.

A client 102 may execute, operate or otherwise provide an application,which can be any type and/or form of software, program, or executableinstructions such as any type and/or form of web browser, web-basedclient, client-server application, a thin-client computing client, anActiveX control, or a Java applet, or any other type and/or form ofexecutable instructions capable of executing on client 102. In someembodiments, the application may be a server-based or a remote-basedapplication executed on behalf of the client 102 on a server 106. In oneembodiments the server 106 may display output to the client 102 usingany thin-client or remote-display protocol, such as the IndependentComputing Architecture (ICA) protocol manufactured by Citrix Systems,Inc. of Ft. Lauderdale, Fla. or the Remote Desktop Protocol (RDP)manufactured by the Microsoft Corporation of Redmond, Wash. Theapplication can use any type of protocol and it can be, for example, anHTTP client, an FTP client, an Oscar client, or a Telnet client. Inother embodiments, the application comprises any type of softwarerelated to VoIP communications, such as a soft IP telephone. In furtherembodiments, the application comprises any application related toreal-time data communications, such as applications for streaming videoand/or audio.

In some embodiments, the server 106 or a server farm 38 may be runningone or more applications, such as an application providing a thin-clientcomputing or remote display presentation application. In one embodiment,the server 106 or server farm 38 executes as an application, any portionof the Citrix Access Suite™ by Citrix Systems, Inc., such as theMetaFrame or Citrix Presentation Server™, and/or any of the Microsoft®Windows Terminal Services manufactured by the Microsoft Corporation. Inone embodiment, the application is an ICA client, developed by CitrixSystems, Inc. of Fort Lauderdale, Fla. In other embodiments, theapplication includes a Remote Desktop (RDP) client, developed byMicrosoft Corporation of Redmond, Wash. Also, the server 106 may run anapplication, which for example, may be an application server providingemail services such as Microsoft Exchange manufactured by the MicrosoftCorporation of Redmond, Wash., a web or Internet server, or a desktopsharing server, or a collaboration server. In some embodiments, any ofthe applications may comprise any type of hosted service or products,such as GoToMeeting™ provided by Citrix Online Division, Inc. of SantaBarbara, Calif., WebEX™ provided by WebEx, Inc. of Santa Clara, Calif.,or Microsoft Office Live Meeting provided by Microsoft Corporation ofRedmond, Wash.

The client 102, server 106, and appliance 200 may be deployed as and/orexecuted on any type and form of computing device, such as a computer,network device or appliance capable of communicating on any type andform of network and performing the operations described herein. FIGS. 1Cand 1D depict block diagrams of a computing device 100 useful forpracticing an embodiment of the client 102, server 106 or appliance 200.As shown in FIGS. 1C and 1D, each computing device 100 includes acentral processing unit 101, and a main memory unit 122. As shown inFIG. 1C, a computing device 100 may include a visual display device 124,a keyboard 126 and/or a pointing device 127, such as a mouse. Eachcomputing device 100 may also include additional optional elements, suchas one or more input/output devices 130 a-130 b (generally referred tousing reference numeral 130), and a cache memory 140 in communicationwith the central processing unit 101.

The central processing unit 101 is any logic circuitry that responds toand processes instructions fetched from the main memory unit 122. Inmany embodiments, the central processing unit is provided by amicroprocessor unit, such as: those manufactured by Intel Corporation ofMountain View, Calif.; those manufactured by Motorola Corporation ofSchaumburg, Ill.; those manufactured by Transmeta Corporation of SantaClara, Calif.; the RS/6000 processor, those manufactured byInternational Business Machines of White Plains, N.Y.; or thosemanufactured by Advanced Micro Devices of Sunnyvale, Calif. Thecomputing device 100 may be based on any of these processors, or anyother processor capable of operating as described herein.

Main memory unit 122 may be one or more memory chips capable of storingdata and allowing any storage location to be directly accessed by themicroprocessor 101, such as Static random access memory (SRAM), BurstSRAM or SynchBurst SRAM (BSRAM), Dynamic random access memory (DRAM),Fast Page Mode DRAM (FPM DRAM), Enhanced DRAM (EDRAM), Extended DataOutput RAM (EDO RAM), Extended Data Output DRAM (EDO DRAM), BurstExtended Data Output DRAM (BEDO DRAM), Enhanced DRAM (EDRAM),synchronous DRAM (SDRAM), JEDEC SRAM, PC100 SDRAM, Double Data RateSDRAM (DDR SDRAM), Enhanced SDRAM (ESDRAM), SyncLink DRAM (SLDRAM),Direct Rambus DRAM (DRDRAM), or Ferroelectric RAM (FRAM). The mainmemory 122 may be based on any of the above described memory chips, orany other available memory chips capable of operating as describedherein. In the embodiment shown in FIG. 1C, the processor 101communicates with main memory 122 via a system bus 150 (described inmore detail below). FIG. 1C depicts an embodiment of a computing device100 in which the processor communicates directly with main memory 122via a memory port 103. For example, in FIG. 1D the main memory 122 maybe DRDRAM.

FIG. 1D depicts an embodiment in which the main processor 101communicates directly with cache memory 140 via a secondary bus,sometimes referred to as a backside bus. In other embodiments, the mainprocessor 101 communicates with cache memory 140 using the system bus150. Cache memory 140 typically has a faster response time than mainmemory 122 and is typically provided by SRAM, BSRAM, or EDRAM. In theembodiment shown in FIG. 1C, the processor 101 communicates with variousI/O devices 130 via a local system bus 150. Various busses may be usedto connect the central processing unit 101 to any of the I/O devices130, including a VESA VL bus, an ISA bus, an EISA bus, a MicroChannelArchitecture (MCA) bus, a PCI bus, a PCI-X bus, a PCI-Express bus, or aNuBus. For embodiments in which the I/O device is a video display 124,the processor 101 may use an Advanced Graphics Port (AGP) to communicatewith the display 124. FIG. 1D depicts an embodiment of a computer 100 inwhich the main processor 101 communicates directly with I/O device 130via HyperTransport, Rapid I/O, or InfiniBand. FIG. 1D also depicts anembodiment in which local busses and direct communication are mixed: theprocessor 101 communicates with I/O device 130 using a localinterconnect bus while communicating with I/O device 130 directly.

The computing device 100 may support any suitable installation device116, such as a floppy disk drive for receiving floppy disks such as3.5-inch, 5.25-inch disks or ZIP disks, a CD-ROM drive, a CD-R/RW drive,a DVD-ROM drive, tape drives of various formats, USB device, hard-driveor any other device suitable for installing software and programs suchas any client agent 120, or portion thereof. The computing device 100may further comprise a storage device 128, such as one or more hard diskdrives or redundant arrays of independent disks, for storing anoperating system and other related software, and for storing applicationsoftware programs such as any program related to the client agent 120.Optionally, any of the installation devices 116 could also be used asthe storage device 128. Additionally, the operating system and thesoftware can be run from a bootable medium, for example, a bootable CD,such as KNOPPIX®, a bootable CD for GNU/Linux that is available as aGNU/Linux distribution from knoppix.net.

Furthermore, the computing device 100 may include a network interface118 to interface to a Local Area Network (LAN), Wide Area Network (WAN)or the Internet through a variety of connections including, but notlimited to, standard telephone lines, LAN or WAN links (e.g., 802.11,T1, T3, 56 kb, X.25), broadband connections (e.g., ISDN, Frame Relay,ATM), wireless connections, or some combination of any or all of theabove. The network interface 118 may comprise a built-in networkadapter, network interface card, PCMCIA network card, card bus networkadapter, wireless network adapter, USB network adapter, modem or anyother device suitable for interfacing the computing device 100 to anytype of network capable of communication and performing the operationsdescribed herein. A wide variety of I/O devices 130 a-130 n may bepresent in the computing device 100. Input devices include keyboards,mice, trackpads, trackballs, microphones, and drawing tablets. Outputdevices include video displays, speakers, inkjet printers, laserprinters, and dye-sublimation printers. The I/O devices 130 may becontrolled by an I/O controller 123 as shown in FIG. 1C. The I/Ocontroller may control one or more I/O devices such as a keyboard 126and a pointing device 127, e.g., a mouse or optical pen. Furthermore, anI/O device may also provide storage 128 and/or an installation medium116 for the computing device 100. In still other embodiments, thecomputing device 100 may provide USB connections to receive handheld USBstorage devices such as the USB Flash Drive line of devices manufacturedby Twintech Industry, Inc. of Los Alamitos, Calif.

In some embodiments, the computing device 100 may comprise or beconnected to multiple display devices 124 a-124 n, which each may be ofthe same or different type and/or form. As such, any of the I/O devices130 a-130 n and/or the I/O controller 123 may comprise any type and/orform of suitable hardware, software, or combination of hardware andsoftware to support, enable or provide for the connection and use ofmultiple display devices 124 a-124 n by the computing device 100. Forexample, the computing device 100 may include any type and/or form ofvideo adapter, video card, driver, and/or library to interface,communicate, connect or otherwise use the display devices 124 a-124 n.In one embodiment, a video adapter may comprise multiple connectors tointerface to multiple display devices 124 a-124 n. In other embodiments,the computing device 100 may include multiple video adapters, with eachvideo adapter connected to one or more of the display devices 124 a-124n. In some embodiments, any portion of the operating system of thecomputing device 100 may be configured for using multiple displays 124a-124 n. In other embodiments, one or more of the display devices 124a-124 n may be provided by one or more other computing devices, such ascomputing devices 100 a and 100 b connected to the computing device 100,for example, via a network. These embodiments may include any type ofsoftware designed and constructed to use another computer's displaydevice as a second display device 124 a for the computing device 100.One ordinarily skilled in the art will recognize and appreciate thevarious ways and embodiments that a computing device 100 may beconfigured to have multiple display devices 124 a-124 n.

In further embodiments, an I/O device 130 may be a bridge 170 betweenthe system bus 150 and an external communication bus, such as a USB bus,an Apple Desktop Bus, an RS-232 serial connection, a SCSI bus, aFireWire bus, a FireWire 800 bus, an Ethernet bus, an AppleTalk bus, aGigabit Ethernet bus, an Asynchronous Transfer Mode bus, a HIPPI bus, aSuper HIPPI bus, a SerialPlus bus, a SCI/LAMP bus, a FibreChannel bus,or a Serial Attached small computer system interface bus.

A computing device 100 of the sort depicted in FIGS. 1C and 1D typicallyoperate under the control of operating systems, which control schedulingof tasks and access to system resources. The computing device 100 can berunning any operating system such as any of the versions of theMicrosoft® Windows operating systems, the different releases of the Unixand Linux operating systems, any version of the Mac OS® for Macintoshcomputers, any embedded operating system, any real-time operatingsystem, any open source operating system, any proprietary operatingsystem, any operating systems for mobile computing devices, or any otheroperating system capable of running on the computing device andperforming the operations described herein. Typical operating systemsinclude: WINDOWS 3.x, WINDOWS 95, WINDOWS 98, WINDOWS 2000, WINDOWS NT3.51, WINDOWS NT 4.0, WINDOWS CE, and WINDOWS XP, all of which aremanufactured by Microsoft Corporation of Redmond, Wash.; MacOS,manufactured by Apple Computer of Cupertino, Calif.; OS/2, manufacturedby International Business Machines of Armonk, N.Y.; and Linux, afreely-available operating system distributed by Caldera Corp. of SaltLake City, Utah, or any type and/or form of a Unix operating system,among others.

In other embodiments, the computing device 100 may have differentprocessors, operating systems, and input devices consistent with thedevice. For example, in one embodiment the computer 100 is a Treo 180,270, 1060, 600 or 650 smart phone manufactured by Palm, Inc. In thisembodiment, the Treo smart phone is operated under the control of thePalmOS operating system and includes a stylus input device as well as afive-way navigator device. Moreover, the computing device 100 can be anyworkstation, desktop computer, laptop or notebook computer, server,handheld computer, mobile telephone, any other computer, or other formof computing or telecommunications device that is capable ofcommunication and that has sufficient processor power and memorycapacity to perform the operations described herein.

B. Appliance Architecture

FIG. 2A illustrates an example embodiment of the appliance 200. Thearchitecture of the appliance 200 in FIG. 2A is provided by way ofillustration only and is not intended to be limiting. As shown in FIG.2, appliance 200 comprises a hardware layer 206 and a software layerdivided into a user space 202 and a kernel space 204.

Hardware layer 206 provides the hardware elements upon which programsand services within kernel space 204 and user space 202 are executed.Hardware layer 206 also provides the structures and elements which allowprograms and services within kernel space 204 and user space 202 tocommunicate data both internally and externally with respect toappliance 200. As shown in FIG. 2, the hardware layer 206 includes aprocessing unit 262 for executing software programs and services, amemory 264 for storing software and data, network ports 266 fortransmitting and receiving data over a network, and an encryptionprocessor 260 for performing functions related to Secure Sockets Layerprocessing of data transmitted and received over the network. In someembodiments, the central processing unit 262 may perform the functionsof the encryption processor 260 in a single processor. Additionally, thehardware layer 206 may comprise multiple processors for each of theprocessing unit 262 and the encryption processor 260. The processor 262may include any of the processors 101 described above in connection withFIGS. 1C and 1D. In some embodiments, the central processing unit 262may perform the functions of the encryption processor 260 in a singleprocessor. Additionally, the hardware layer 206 may comprise multipleprocessors for each of the processing unit 262 and the encryptionprocessor 260. For example, in one embodiment, the appliance 200comprises a first processor 262 and a second processor 262′. In otherembodiments, the processor 262 or 262′ comprises a multi-core processor.

Although the hardware layer 206 of appliance 200 is generallyillustrated with an encryption processor 260, processor 260 may be aprocessor for performing functions related to any encryption protocol,such as the Secure Socket Layer (SSL) or Transport Layer Security (TLS)protocol. In some embodiments, the processor 260 may be a generalpurpose processor (GPP), and in further embodiments, may be haveexecutable instructions for performing processing of any securityrelated protocol.

Although the hardware layer 206 of appliance 200 is illustrated withcertain elements in FIG. 2, the hardware portions or components ofappliance 200 may comprise any type and form of elements, hardware orsoftware, of a computing device, such as the computing device 100illustrated and discussed herein in conjunction with FIGS. 1C and 1D. Insome embodiments, the appliance 200 may comprise a server, gateway,router, switch, bridge or other type of computing or network device, andhave any hardware and/or software elements associated therewith.

The operating system of appliance 200 allocates, manages, or otherwisesegregates the available system memory into kernel space 204 and userspace 204. In example software architecture 200, the operating systemmay be any type and/or form of Unix operating system although theinvention is not so limited. As such, the appliance 200 can be runningany operating system such as any of the versions of the Microsoft®Windows operating systems, the different releases of the Unix and Linuxoperating systems, any version of the Mac OS® for Macintosh computers,any embedded operating system, any network operating system, anyreal-time operating system, any open source operating system, anyproprietary operating system, any operating systems for mobile computingdevices or network devices, or any other operating system capable ofrunning on the appliance 200 and performing the operations describedherein.

The kernel space 204 is reserved for running the kernel 230, includingany device drivers, kernel extensions or other kernel related software.As known to those skilled in the art, the kernel 230 is the core of theoperating system, and provides access, control, and management ofresources and hardware-related elements of the application 104. Inaccordance with an embodiment of the appliance 200, the kernel space 204also includes a number of network services or processes working inconjunction with a cache manager 232. sometimes also referred to as theintegrated cache, the benefits of which are described in detail furtherherein. Additionally, the embodiment of the kernel 230 will depend onthe embodiment of the operating system installed, configured, orotherwise used by the device 200.

In one embodiment, the device 200 comprises one network stack 267, suchas a TCP/IP based stack, for communicating with the client 102 and/orthe server 106. In one embodiment, the network stack 267 is used tocommunicate with a first network, such as network 108, and a secondnetwork 110. In some embodiments, the device 200 terminates a firsttransport layer connection, such as a TCP connection of a client 102,and establishes a second transport layer connection to a server 106 foruse by the client 102, e.g., the second transport layer connection isterminated at the appliance 200 and the server 106. The first and secondtransport layer connections may be established via a single networkstack 267. In other embodiments, the device 200 may comprise multiplenetwork stacks, for example 267 and 267′, and the first transport layerconnection may be established or terminated at one network stack 267,and the second transport layer connection on the second network stack267′. For example, one network stack may be for receiving andtransmitting network packet on a first network, and another networkstack for receiving and transmitting network packets on a secondnetwork. In one embodiment, the network stack 267 comprises a buffer 243for queuing one or more network packets for transmission by theappliance 200.

As shown in FIG. 2, the kernel space 204 includes the cache manager 232,a high-speed layer 2-7 integrated packet engine 240, an encryptionengine 234, a policy engine 236 and multi-protocol compression logic238. Running these components or processes 232, 240, 234, 236 and 238 inkernel space 204 or kernel mode instead of the user space 202 improvesthe performance of each of these components, alone and in combination.Kernel operation means that these components or processes 232, 240, 234,236 and 238 run in the core address space of the operating system of thedevice 200. For example, running the encryption engine 234 in kernelmode improves encryption performance by moving encryption and decryptionoperations to the kernel, thereby reducing the number of transitionsbetween the memory space or a kernel thread in kernel mode and thememory space or a thread in user mode. For example, data obtained inkernel mode may not need to be passed or copied to a process or threadrunning in user mode, such as from a kernel level data structure to auser level data structure. In another aspect, the number of contextswitches between kernel mode and user mode are also reduced.Additionally, synchronization of and communications between any of thecomponents or processes 232, 240, 235, 236 and 238 can be performed moreefficiently in the kernel space 204.

In some embodiments, any portion of the components 232, 240, 234, 236and 238 may run or operate in the kernel space 204, while other portionsof these components 232, 240, 234, 236 and 238 may run or operate inuser space 202. In one embodiment, the appliance 200 uses a kernel-leveldata structure providing access to any portion of one or more networkpackets, for example, a network packet comprising a request from aclient 102 or a response from a server 106. In some embodiments, thekernel-level data structure may be obtained by the packet engine 240 viaa transport layer driver interface or filter to the network stack 267.The kernel-level data structure may comprise any interface and/or dataaccessible via the kernel space 204 related to the network stack 267,network traffic or packets received or transmitted by the network stack267. In other embodiments, the kernel-level data structure may be usedby any of the components or processes 232, 240, 234, 236 and 238 toperform the desired operation of the component or process. In oneembodiment, a component 232, 240, 234, 236 and 238 is running in kernelmode 204 when using the kernel-level data structure, while in anotherembodiment, the component 232, 240, 234, 236 and 238 is running in usermode when using the kernel-level data structure. In some embodiments,the kernel-level data structure may be copied or passed to a secondkernel-level data structure, or any desired user-level data structure.

The cache manager 232 may comprise software, hardware or any combinationof software and hardware to provide cache access, control and managementof any type and form of content, such as objects or dynamicallygenerated objects served by the originating servers 106. The data,objects or content processed and stored by the cache manager 232 maycomprise data in any format, such as a markup language, or communicatedvia any protocol. In some embodiments, the cache manager 232 duplicatesoriginal data stored elsewhere or data previously computed, generated ortransmitted, in which the original data may require longer access timeto fetch, compute or otherwise obtain relative to reading a cache memoryelement. Once the data is stored in the cache memory element, future usecan be made by accessing the cached copy rather than refetching orrecomputing the original data, thereby reducing the access time. In someembodiments, the cache memory element that comprise a data object inmemory 264 of device 200. In other embodiments, the cache memory elementmay comprise memory having a faster access time than memory 264. Inanother embodiment, the cache memory element may comprise any type andform of storage element of the device 200, such as a portion of a harddisk. In some embodiments, the processing unit 262 may provide cachememory for use by the cache manager 232. In yet further embodiments, thecache manager 232 may use any portion and combination of memory,storage, or the processing unit for caching data, objects, and othercontent.

Furthermore, the cache manager 232 includes any logic, functions, rules,or operations to perform any embodiments of the techniques of theappliance 200 described herein. For example, the cache manager 232includes logic or functionality to invalidate objects based on theexpiration of an invalidation time period or upon receipt of aninvalidation command from a client 102 or server 106. In someembodiments, the cache manager 232 may operate as a program, service,process or task executing in the kernel space 204, and in otherembodiments, in the user space 202. In one embodiment, a first portionof the cache manager 232 executes in the user space 202 while a secondportion executes in the kernel space 204. In some embodiments, the cachemanager 232 can comprise any type of general purpose processor (GPP), orany other type of integrated circuit, such as a Field Programmable GateArray (FPGA), Programmable Logic Device (PLD), or Application SpecificIntegrated Circuit (ASIC).

The policy engine 236 may include, for example, an intelligentstatistical engine or other programmable application(s). In oneembodiment, the policy engine 236 provides a configuration mechanism toallow a user to identifying, specify, define or configure a cachingpolicy. Policy engine 236, in some embodiments, also has access tomemory to support data structures such as lookup tables or hash tablesto enable user-selected caching policy decisions. In other embodiments,the policy engine 236 may comprise any logic, rules, functions oroperations to determine and provide access, control and management ofobjects, data or content being cached by the appliance 200 in additionto access, control and management of security, network traffic, networkaccess, compression or any other function or operation performed by theappliance 200. Further examples of specific caching policies are furtherdescribed herein.

The encryption engine 234 comprises any logic, business rules, functionsor operations for handling the processing of any security relatedprotocol, such as SSL or TLS, or any function related thereto. Forexample, the encryption engine 234 encrypts and decrypts networkpackets, or any portion thereof, communicated via the appliance 200. Theencryption engine 234 may also setup or establish SSL or TLS connectionson behalf of the client 102 a-102 n, server 106 a-106 n, or appliance200. As such, the encryption engine 234 provides offloading andacceleration of SSL processing. In one embodiment, the encryption engine234 uses a tunneling protocol to provide a virtual private networkbetween a client 102 a-102 n and a server 106 a-106 n. In someembodiments, the encryption engine 234 is in communication with theEncryption processor 260. In other embodiments, the encryption engine234 comprises executable instructions running on the Encryptionprocessor 260.

The multi-protocol compression engine 238 comprises any logic, businessrules, function or operations for compressing one or more protocols of anetwork packet, such as any of the protocols used by the network stack267 of the device 200. In one embodiment, multi-protocol compressionengine 238 compresses bi-directionally between clients 102 a-102 n andservers 106 a-106 n any TCP/IP based protocol, including MessagingApplication Programming Interface (MAPI) (email), File Transfer Protocol(FTP), HyperText Transfer Protocol (HTTP), Common Internet File System(CIFS) protocol (file transfer), Independent Computing Architecture(ICA) protocol, Remote Desktop Protocol (RDP), Wireless ApplicationProtocol (WAP), Mobile IP protocol, and Voice Over IP (VoIP) protocol.In other embodiments, multi-protocol compression engine 238 providescompression of Hypertext Markup Language (HTML) based protocols and insome embodiments, provides compression of any markup languages, such asthe Extensible Markup Language (XML). In one embodiment, themulti-protocol compression engine 238 provides compression of anyhigh-performance protocol, such as any protocol designed for appliance200 to appliance 200 communications. In another embodiment, themulti-protocol compression engine 238 compresses any payload of or anycommunication using a modified transport control protocol, such asTransaction TCP (T/TCP), TCP with selection acknowledgements (TCP-SACK),TCP with large windows (TCP-LW), a congestion prediction protocol suchas the TCP-Vegas protocol, and a TCP spoofing protocol.

As such, the multi-protocol compression engine 238 acceleratesperformance for users accessing applications via desktop clients, e.g.,Microsoft Outlook and non-Web thin clients, such as any client launchedby popular enterprise applications like Oracle, SAP and Siebel, and evenmobile clients, such as the Pocket PC. In some embodiments, themulti-protocol compression engine 238 by executing in the kernel mode204 and integrating with packet processing engine 240 accessing thenetwork stack 267 is able to compress any of the protocols carried bythe TCP/IP protocol, such as any application layer protocol.

High speed layer 2-7 integrated packet engine 240, also generallyreferred to as a packet processing engine or packet engine, isresponsible for managing the kernel-level processing of packets receivedand transmitted by appliance 200 via network ports 266. The high speedlayer 2-7 integrated packet engine 240 may comprise a buffer for queuingone or more network packets during processing, such as for receipt of anetwork packet or transmission of a network packer. Additionally, thehigh speed layer 2-7 integrated packet engine 240 is in communicationwith one or more network stacks 267 to send and receive network packetsvia network ports 266. The high speed layer 2-7 integrated packet engine240 works in conjunction with encryption engine 234, cache manager 232,policy engine 236 and multi-protocol compression logic 238. Inparticular, encryption engine 234 is configured to perform SSLprocessing of packets, policy engine 236 is configured to performfunctions related to traffic management such as request-level contentswitching and request-level cache redirection, and multi-protocolcompression logic 238 is configured to perform functions related tocompression and decompression of data.

The high speed layer 2-7 integrated packet engine 240 includes a packetprocessing timer 242. In one embodiment, the packet processing timer 242provides one or more time intervals to trigger the processing ofincoming, i.e., received, or outgoing, i.e., transmitted, networkpackets. In some embodiments, the high speed layer 2-7 integrated packetengine 240 processes network packets responsive to the timer 242. Thepacket processing timer 242 provides any type and form of signal to thepacket engine 240 to notify, trigger, or communicate a time relatedevent, interval or occurrence. In many embodiments, the packetprocessing timer 242 operates in the order of milliseconds, such as forexample 100 ms, 50 ms or 25 ms. For example, in some embodiments, thepacket processing timer 242 provides time intervals or otherwise causesa network packet to be processed by the high speed layer 2-7 integratedpacket engine 240 at a 10 ms time interval, while in other embodiments,at a 5 ms time interval, and still yet in further embodiments, as shortas a 3, 2, or 1 ms time interval. The high speed layer 2-7 integratedpacket engine 240 may be interfaced, integrated or in communication withthe encryption engine 234, cache manager 232, policy engine 236 andmulti-protocol compression engine 238 during operation. As such, any ofthe logic, functions, or operations of the encryption engine 234, cachemanager 232, policy engine 236 and multi-protocol compression logic 238may be performed responsive to the packet processing timer 242 and/orthe packet engine 240. Therefore, any of the logic, functions, oroperations of the encryption engine 234, cache manager 232, policyengine 236 and multi-protocol compression logic 238 may be performed atthe granularity of time intervals provided via the packet processingtimer 242, for example, at a time interval of less than or equal to 10ms. For example, in one embodiment, the cache manager 232 may performinvalidation of any cached objects responsive to the high speed layer2-7 integrated packet engine 240 and/or the packet processing timer 242.In another embodiment, the expiry or invalidation time of a cachedobject can be set to the same order of granularity as the time intervalof the packet processing timer 242, such as at every 10 ms.

In contrast to kernel space 204, user space 202 is the memory area orportion of the operating system used by user mode applications orprograms otherwise running in user mode. A user mode application may notaccess kernel space 204 directly and uses service calls in order toaccess kernel services. As shown in FIG. 2, user space 202 of appliance200 includes a graphical user interface (GUI) 210, a command lineinterface (CLI) 212, shell services 214, health monitoring program 216,and daemon services 218. GUI 210 and CLI 212 provide a means by which asystem administrator or other user can interact with and control theoperation of appliance 200, such as via the operating system of theappliance 200 and either is user space 202 or kernel space 204. The GUI210 may be any type and form of graphical user interface and may bepresented via text, graphical or otherwise, by any type of program orapplication, such as a browser. The CLI 212 may be any type and form ofcommand line or text-based interface, such as a command line provided bythe operating system. For example, the CLI 212 may comprise a shell,which is a tool to enable users to interact with the operating system.In some embodiments, the CLI 212 may be provided via a bash, csh, tcsh,or ksh type shell. The shell services 214 comprises the programs,services, tasks, processes or executable instructions to supportinteraction with the appliance 200 or operating system by a user via theGUI 210 and/or CLI 212.

Health monitoring program 216 is used to monitor, check, report andensure that network systems are functioning properly and that users arereceiving requested content over a network. Health monitoring program216 comprises one or more programs, services, tasks, processes orexecutable instructions to provide logic, rules, functions or operationsfor monitoring any activity of the appliance 200. In some embodiments,the health monitoring program 216 intercepts and inspects any networktraffic passed via the appliance 200. In other embodiments, the healthmonitoring program 216 interfaces by any suitable means and/ormechanisms with one or more of the following: the encryption engine 234,cache manager 232, policy engine 236, multi-protocol compression logic238, packet engine 240, daemon services 218, and shell services 214. Assuch, the health monitoring program 216 may call any applicationprogramming interface (API) to determine a state, status, or health ofany portion of the appliance 200. For example, the health monitoringprogram 216 may ping or send a status inquiry on a periodic basis tocheck if a program, process, service or task is active and currentlyrunning. In another example, the health monitoring program 216 may checkany status, error or history logs provided by any program, process,service or task to determine any condition, status or error with anyportion of the appliance 200.

Daemon services 218 are programs that run continuously or in thebackground and handle periodic service requests received by appliance200. In some embodiments, a daemon service may forward the requests toother programs or processes, such as another daemon service 218 asappropriate. As known to those skilled in the art, a daemon service 218may run unattended to perform continuous or periodic system widefunctions, such as network control, or to perform any desired task. Insome embodiments, one or more daemon services 218 run in the user space202, while in other embodiments, one or more daemon services 218 run inthe kernel space.

Referring now to FIG. 2B, another embodiment of the appliance 200 isdepicted. In brief overview, the appliance 200 provides one or more ofthe following services, functionality or operations: SSL VPNconnectivity 280, switching/load balancing 284, Domain Name Serviceresolution 286, acceleration 288 and an application firewall 290 forcommunications between one or more clients 102 and one or more servers106. In one embodiment, the appliance 200 comprises any of the networkdevices manufactured by Citrix Systems, Inc. of Ft. Lauderdale Fla.,referred to as Citrix NetScaler devices. Each of the servers 106 mayprovide one or more network related services 270 a-270 n (referred to asservices 270). For example, a server 106 may provide an http service270. The appliance 200 comprises one or more virtual servers or virtualinternet protocol servers, referred to as a vServer, VIP server, or justVIP 275 a-275 n (also referred herein as vServer 275). The vServer 275receives, intercepts or otherwise processes communications between aclient 102 and a server 106 in accordance with the configuration andoperations of the appliance 200.

The vServer 275 may comprise software, hardware or any combination ofsoftware and hardware. The vServer 275 may comprise any type and form ofprogram, service, task, process or executable instructions operating inuser mode 202, kernel mode 204 or any combination thereof in theappliance 200. The vServer 275 includes any logic, functions, rules, oroperations to perform any embodiments of the techniques describedherein, such as SSL VPN 280, switching/load balancing 284, Domain NameService resolution 286, acceleration 288 and an application firewall290. In some embodiments, the vServer 275 establishes a connection to aservice 270 of a server 106. The service 275 may comprise any program,application, process, task or set of executable instructions capable ofconnecting to and communicating to the appliance 200, client 102 orvServer 275. For example, the service 275 may comprise a web server,http server, ftp, email or database server. In some embodiments, theservice 270 is a daemon process or network driver for listening,receiving and/or sending communications for an application, such asemail, database or an enterprise application. In some embodiments, theservice 270 may communicate on a specific IP address, or IP address andport.

In some embodiments, the vServer 275 applies one or more policies of thepolicy engine 236 to network communications between the client 102 andserver 106. In one embodiment, the policies are associated with aVServer 275. In another embodiment, the policies are based on a user, ora group of users. In yet another embodiment, a policy is global andapplies to one or more vServers 275 a-275 n, and any user or group ofusers communicating via the appliance 200. In some embodiments, thepolicies of the policy engine have conditions upon which the policy isapplied based on any content of the communication, such as internetprotocol address, port, protocol type, header or fields in a packet, orthe context of the communication, such as user, group of the user,vServer 275, transport layer connection, and/or identification orattributes of the client 102 or server 106.

In other embodiments, the appliance 200 communicates or interfaces withthe policy engine 236 to determine authentication and/or authorizationof a remote user or a remote client 102 to access the computingenvironment 15, application, and/or data file from a server 106. Inanother embodiment, the appliance 200 communicates or interfaces withthe policy engine 236 to determine authentication and/or authorizationof a remote user or a remote client 102 to have the application deliverysystem 190 deliver one or more of the computing environment 15,application, and/or data file. In yet another embodiment, the appliance200 establishes a VPN or SSL VPN connection based on the policy engine's236 authentication and/or authorization of a remote user or a remoteclient 103 In one embodiment, the appliance 102 controls the flow ofnetwork traffic and communication sessions based on policies of thepolicy engine 236. For example, the appliance 200 may control the accessto a computing environment 15, application or data file based on thepolicy engine 236.

In some embodiments, the vServer 275 establishes a transport layerconnection, such as a TCP or UDP connection with a client 102 via theclient agent 120. In one embodiment, the vServer 275 listens for andreceives communications from the client 102. In other embodiments, thevServer 275 establishes a transport layer connection, such as a TCP orUDP connection with a client server 106. In one embodiment, the vServer275 establishes the transport layer connection to an internet protocoladdress and port of a server 270 running on the server 106. In anotherembodiment, the vServer 275 associates a first transport layerconnection to a client 102 with a second transport layer connection tothe server 106. In some embodiments, a vServer 275 establishes a pool oftransport layer connections to a server 106 and multiplexes clientrequests via the pooled transport layer connections.

In some embodiments, the appliance 200 provides a SSL VPN connection 280between a client 102 and a server 106. For example, a client 102 on afirst network 102 requests to establish a connection to a server 106 ona second network 104′. In some embodiments, the second network 104′ isnot routable from the first network 104. In other embodiments, theclient 102 is on a public network 104 and the server 106 is on a privatenetwork 104′, such as a corporate network. In one embodiment, the clientagent 120 intercepts communications of the client 102 on the firstnetwork 104, encrypts the communications, and transmits thecommunications via a first transport layer connection to the appliance200. The appliance 200 associates the first transport layer connectionon the first network 104 to a second transport layer connection to theserver 106 on the second network 104. The appliance 200 receives theintercepted communication from the client agent 102, decrypts thecommunications, and transmits the communication to the server 106 on thesecond network 104 via the second transport layer connection. The secondtransport layer connection may be a pooled transport layer connection.As such, the appliance 200 provides an end-to-end secure transport layerconnection for the client 102 between the two networks 104, 104′.

In one embodiment, the appliance 200 hosts an intranet internet protocolor intranetIP 282 address of the client 102 on the virtual privatenetwork 104. The client 102 has a local network identifier, such as aninternet protocol (IP) address and/or host name on the first network104. When connected to the second network 104′ via the appliance 200,the appliance 200 establishes, assigns or otherwise provides anIntranetIP, which is network identifier, such as IP address and/or hostname, for the client 102 on the second network 104′. The appliance 200listens for and receives on the second or private network 104′ for anycommunications directed towards the client 102 using the client'sestablished IntranetIP 282. In one embodiment, the appliance 200 acts asor on behalf of the client 102 on the second private network 104. Forexample, in another embodiment, a vServer 275 listens for and respondsto communications to the IntranetIP 282 of the client 102. In someembodiments, if a computing device 100 on the second network 104′transmits a request, the appliance 200 processes the request as if itwere the client 102. For example, the appliance 200 may respond to aping to the client's IntranetIP 282. In another example, the appliancemay establish a connection, such as a TCP or UDP connection, withcomputing device 100 on the second network 104 requesting a connectionwith the client's IntranetIP 282.

In some embodiments, the appliance 200 provides one or more of thefollowing acceleration techniques 288 to communications between theclient 102 and server 106: 1) compression; 2) decompression; 3)Transmission Control Protocol pooling; 4) Transmission Control Protocolmultiplexing; 5) Transmission Control Protocol buffering; and 6)caching. In one embodiment, the appliance 200 relieves servers 106 ofmuch of the processing load caused by repeatedly opening and closingtransport layers connections to clients 102 by opening one or moretransport layer connections with each server 106 and maintaining theseconnections to allow repeated data accesses by clients via the Internet.This technique is referred to herein as “connection pooling”.

In some embodiments, in order to seamlessly splice communications from aclient 102 to a server 106 via a pooled transport layer connection, theappliance 200 translates or multiplexes communications by modifyingsequence number and acknowledgment numbers at the transport layerprotocol level. This is referred to as “connection multiplexing”. Insome embodiments, no application layer protocol interaction is required.For example, in the case of an in-bound packet (that is, a packetreceived from a client 102), the source network address of the packet ischanged to that of an output port of appliance 200, and the destinationnetwork address is changed to that of the intended server. In the caseof an outbound packet (that is, one received from a server 106), thesource network address is changed from that of the server 106 to that ofan output port of appliance 200 and the destination address is changedfrom that of appliance 200 to that of the requesting client 102. Thesequence numbers and acknowledgment numbers of the packet are alsotranslated to sequence numbers and acknowledgement expected by theclient 102 on the appliance's 200 transport layer connection to theclient 102. In some embodiments, the packet checksum of the transportlayer protocol is recalculated to account for these translations.

In another embodiment, the appliance 200 provides switching orload-balancing functionality 284 for communications between the client102 and server 106. In some embodiments, the appliance 200 distributestraffic and directs client requests to a server 106 based on layer 4 orapplication-layer request data. In one embodiment, although the networklayer or layer 2 of the network packet identifies a destination server106, the appliance 200 determines the server 106 to distribute thenetwork packet by application information and data carried as payload ofthe transport layer packet. In one embodiment, the health monitoringprograms 216 of the appliance 200 monitor the health of servers todetermine the server 106 for which to distribute a client's request. Insome embodiments, if the appliance 200 detects a server 106 is notavailable or has a load over a predetermined threshold, the appliance200 can direct or distribute client requests to another server 106.

In some embodiments, the appliance 200 acts as a Domain Name Service(DNS) resolver or otherwise provides resolution of a DNS request fromclients 102. In some embodiments, the appliance intercepts' a DNSrequest transmitted by the client 102. In one embodiment, the appliance200 responds to a client's DNS request with an IP address of or hostedby the appliance 200. In this embodiment, the client 102 transmitsnetwork communication for the domain name to the appliance 200. Inanother embodiment, the appliance 200 responds to a client's DNS requestwith an IP address of or hosted by a second appliance 200′. In someembodiments, the appliance 200 responds to a client's DNS request withan IP address of a server 106 determined by the appliance 200.

In yet another embodiment, the appliance 200 provides applicationfirewall functionality 290 for communications between the client 102 andserver 106. In one embodiment, the policy engine 236 provides rules fordetecting and blocking illegitimate requests. In some embodiments, theapplication firewall 290 protects against denial of service (DoS)attacks. In other embodiments, the appliance inspects the content ofintercepted requests to identify and block application-based attacks. Insome embodiments, the rules/policy engine 236 comprises one or moreapplication firewall or security control policies for providingprotections against various classes and types of web or Internet basedvulnerabilities, such as one or more of the following: 1) bufferoverflow, 2) CGI-BIN parameter manipulation, 3) form/hidden fieldmanipulation, 4) forceful browsing, 5) cookie or session poisoning, 6)broken access control list (ACLs) or weak passwords, 7) cross-sitescripting (XSS), 8) command injection, 9) SQL injection, 10) errortriggering sensitive information leak, 11) insecure use of cryptography,12) server misconfiguration, 13) back doors and debug options, 14)website defacement, 15) platform or operating systems vulnerabilities,and 16) zero-day exploits. In an embodiment, the application firewall290 provides HTML form field protection in the form of inspecting oranalyzing the network communication for one or more of the following: 1)required fields are returned, 2) no added field allowed, 3) read-onlyand hidden field enforcement, 4) drop-down list and radio button fieldconformance, and 5) form-field max-length enforcement. In someembodiments, the application firewall 290 ensures cookies are notmodified. In other embodiments, the application firewall 290 protectsagainst forceful browsing by enforcing legal URLs.

In still yet other embodiments, the application firewall 290 protectsany confidential information contained in the network communication. Theapplication firewall 290 may inspect or analyze any networkcommunication in accordance with the rules or polices of the engine 236to identify any confidential information in any field of the networkpacket. In some embodiments, the application firewall 290 identifies inthe network communication one or more occurrences of a credit cardnumber, password, social security number, name, patient code, contactinformation, and age. The encoded portion of the network communicationmay comprise these occurrences or the confidential information. Based onthese occurrences, in one embodiment, the application firewall 290 maytake a policy action on the network communication, such as preventtransmission of the network communication. In another embodiment, theapplication firewall 290 may rewrite, remove or otherwise mask suchidentified occurrence or confidential information.

C. Client Agent

Referring now to FIG. 3, an embodiment of the client agent 120 isdepicted. The client 102 includes a client agent 120 for establishingand exchanging communications with the appliance 200 and/or server 106via a network 104. In brief overview, the client 102 operates oncomputing device 100 having an operating system with a kernel mode 302and a user mode 303, and a network stack 310 with one or more layers 310a-310 b. The client 102 may have installed and/or execute one or moreapplications. In some embodiments, one or more applications maycommunicate via the network stack 310 to a network 104. One of theapplications, such as a web browser, may also include a first program322. For example, the first program 322 may be used in some embodimentsto install and/or execute the client agent 120, or any portion thereof.The client agent 120 includes an interception mechanism, or interceptor350, for intercepting network communications from the network stack 310from the one or more applications.

The network stack 310 of the client 102 may comprise any type and formof software, or hardware, or any combinations thereof, for providingconnectivity to and communications with a network. In one embodiment,the network stack 310 comprises a software implementation for a networkprotocol suite. The network stack 310 may comprise one or more networklayers, such as any networks layers of the Open Systems Interconnection(OSI) communications model as those skilled in the art recognize andappreciate. As such, the network stack 310 may comprise any type andform of protocols for any of the following layers of the OSI model: 1)physical link layer, 2) data link layer, 3) network layer, 4) transportlayer, 5) session layer, 6) presentation layer, and 7) applicationlayer. In one embodiment, the network stack 310 may comprise a transportcontrol protocol (TCP) over the network layer protocol of the internetprotocol (IP), generally referred to as TCP/IP. In some embodiments, theTCP/IP protocol may be carried over the Ethernet protocol, which maycomprise any of the family of IEEE wide-area-network (WAN) orlocal-area-network (LAN) protocols, such as those protocols covered bythe IEEE 802.3. In some embodiments, the network stack 310 comprises anytype and form of a wireless protocol, such as IEEE 802.11 and/or mobileinternet protocol.

In view of a TCP/IP based network, any TCP/IP based protocol may beused, including Messaging Application Programming Interface (MAPI)(email), File Transfer Protocol (FTP), HyperText Transfer Protocol(HTTP), Common Internet File System (CIFS) protocol (file transfer),Independent Computing Architecture (ICA) protocol, Remote DesktopProtocol (RDP), Wireless Application Protocol (WAP), Mobile IP protocol,and Voice Over IP (VoIP) protocol. In another embodiment, the networkstack 310 comprises any type and form of transport control protocol,such as a modified transport control protocol, for example a TransactionTCP (T/TCP), TCP with selection acknowledgements (TCP-SACK), TCP withlarge windows (TCP-LW), a congestion prediction protocol such as theTCP-Vegas protocol, and a TCP spoofing protocol. In other embodiments,any type and form of user datagram protocol (UDP), such as UDP over IP,may be used by the network stack 310, such as for voice communicationsor real-time data communications.

Furthermore, the network stack 310 may include one or more networkdrivers supporting the one or more layers, such as a TCP driver or anetwork layer driver. The network drivers may be included as part of theoperating system of the computing device 100 or as part of any networkinterface cards or other network access components of the computingdevice 100. In some embodiments, any of the network drivers of thenetwork stack 310 may be customized, modified or adapted to provide acustom or modified portion of the network stack 310 in support of any ofthe techniques described herein. In other embodiments, the accelerationprogram 120 is designed and constructed to operate with or work inconjunction with the network stack 310 installed or otherwise providedby the operating system of the client 102.

The network stack 310 comprises any type and form of interfaces forreceiving, obtaining, providing or otherwise accessing any informationand data related to network communications of the client 102. In oneembodiment, an interface to the network stack 310 comprises anapplication programming interface (API). The interface may also compriseany function call, hooking or filtering mechanism, event or call backmechanism, or any type of interfacing technique. The network stack 310via the interface may receive or provide any type and form of datastructure, such as an object, related to functionality or operation ofthe network stack 310. For example, the data structure may compriseinformation and data related to a network packet or one or more networkpackets. In some embodiments, the data structure comprises a portion ofthe network packet processed at a protocol layer of the network stack310, such as a network packet of the transport layer. In someembodiments, the data structure 325 comprises a kernel-level datastructure, while in other embodiments, the data structure 325 comprisesa user-mode data structure. A kernel-level data structure may comprise adata structure obtained or related to a portion of the network stack 310operating in kernel-mode 302, or a network driver or other softwarerunning in kernel-mode 302, or any data structure obtained or receivedby a service, process, task, thread or other executable instructionsrunning or operating in kernel-mode of the operating system.

Additionally, some portions of the network stack 310 may execute oroperate in kernel-mode 302, for example, the data link or network layer,while other portions execute or operate in user-mode 303, such as anapplication layer of the network stack 310. For example, a first portion310 a of the network stack may provide user-mode access to the networkstack 310 to an application while a second portion 310 a of the networkstack 310 provides access to a network. In some embodiments, a firstportion 310 a of the network stack may comprise one or more upper layersof the network stack 310, such as any of layers 5-7. In otherembodiments, a second portion 310 b of the network stack 310 comprisesone or more lower layers, such as any of layers 1-4. Each of the firstportion 310 a and second portion 310 b of the network stack 310 maycomprise any portion of the network stack 310, at any one or morenetwork layers, in user-mode 203, kernel-mode, 202, or combinationsthereof, or at any portion of a network layer or interface point to anetwork layer or any portion of or interface point to the user-mode 203and kernel-mode 203.

The interceptor 350 may comprise software, hardware, or any combinationof software and hardware. In one embodiment, the interceptor 350intercept a network communication at any point in the network stack 310,and redirects or transmits the network communication to a destinationdesired, managed or controlled by the interceptor 350 or client agent120. For example, the interceptor 350 may intercept a networkcommunication of a network stack 310 of a first network and transmit thenetwork communication to the appliance 200 for transmission on a secondnetwork 104. In some embodiments, the interceptor 350 comprises any typeinterceptor 350 comprises a driver, such as a network driver constructedand designed to interface and work with the network stack 310. In someembodiments, the client agent 120 and/or interceptor 350 operates at oneor more layers of the network stack 310, such as at the transport layer.In one embodiment, the interceptor 350 comprises a filter driver,hooking mechanism, or any form and type of suitable network driverinterface that interfaces to the transport layer of the network stack,such as via the transport driver interface (TDI). In some embodiments,the interceptor 350 interfaces to a first protocol layer, such as thetransport layer and another protocol layer, such as any layer above thetransport protocol layer, for example, an application protocol layer. Inone embodiment, the interceptor 350 may comprise a driver complying withthe Network Driver Interface Specification (NDIS), or a NDIS driver. Inanother embodiment, the interceptor 350 may comprise a min-filter or amini-port driver. In one embodiment, the interceptor 350, or portionthereof, operates in kernel-mode 202. In another embodiment, theinterceptor 350, or portion thereof, operates in user-mode 203. In someembodiments, a portion of the interceptor 350 operates in kernel-mode202 while another portion of the interceptor 350 operates in user-mode203. In other embodiments, the client agent 120 operates in user-mode203 but interfaces via the interceptor 350 to a kernel-mode driver,process, service, task or portion of the operating system, such as toobtain a kernel-level data structure 225. In further embodiments, theinterceptor 350 is a user-mode application or program, such asapplication.

In one embodiment, the interceptor 350 intercepts any transport layerconnection requests. In these embodiments, the interceptor 350 executetransport layer application programming interface (API) calls to set thedestination information, such as destination IP address and/or port to adesired location for the location. In this manner, the interceptor 350intercepts and redirects the transport layer connection to a IP addressand port controlled or managed by the interceptor 350 or client agent120. In one embodiment, the interceptor 350 sets the destinationinformation for the connection to a local IP address and port of theclient 102 on which the client agent 120 is listening. For example, theclient agent 120 may comprise a proxy service listening on a local IPaddress and port for redirected transport layer communications. In someembodiments, the client agent 120 then communicates the redirectedtransport layer communication to the appliance 200.

In some embodiments, the interceptor 350 intercepts a Domain NameService (DNS) request. In one embodiment, the client agent 120 and/orinterceptor 350 resolves the DNS request. In another embodiment, theinterceptor transmits the intercepted DNS request to the appliance 200for DNS resolution. In one embodiment, the appliance 200 resolves theDNS request and communicates the DNS response to the client agent 120.In some embodiments, the appliance 200 resolves the DNS request viaanother appliance 200′ or a DNS server 106.

In yet another embodiment, the client agent 120 may comprise two agents120 and 120′. In one embodiment, a first agent 120 may comprise aninterceptor 350 operating at the network layer of the network stack 310.In some embodiments, the first agent 120 intercepts network layerrequests such as Internet Control Message Protocol (ICMP) requests(e.g., ping and traceroute). In other embodiments, the second agent 120′may operate at the transport layer and intercept transport layercommunications. In some embodiments, the first agent 120 interceptscommunications at one layer of the network stack 210 and interfaces withor communicates the intercepted communication to the second agent 120′.

The client agent 120 and/or interceptor 350 may operate at or interfacewith a protocol layer in a manner transparent to any other protocollayer of the network stack 310. For example, in one embodiment, theinterceptor 350 operates or interfaces with the transport layer of thenetwork stack 310 transparently to any protocol layer below thetransport layer, such as the network layer, and any protocol layer abovethe transport layer, such as the session, presentation or applicationlayer protocols. This allows the other protocol layers of the networkstack 310 to operate as desired and without modification for using theinterceptor 350. As such, the client agent 120 and/or interceptor 350can interface with the transport layer to secure, optimize, accelerate,route or load-balance any communications provided via any protocolcarried by the transport layer, such as any application layer protocolover TCP/IP.

Furthermore, the client agent 120 and/or interceptor may operate at orinterface with the network stack 310 in a manner transparent to anyapplication, a user of the client 102, and any other computing device,such as a server, in communications with the client 102. The clientagent 120 and/or interceptor 350 may be installed and/or executed on theclient 102 in a manner without modification of an application. In someembodiments, the user of the client 102 or a computing device incommunications with the client 102 are not aware of the existence,execution or operation of the client agent 120 and/or interceptor 350.As such, in some embodiments, the client agent 120 and/or interceptor350 is installed, executed, and/or operated transparently to anapplication, user of the client 102, another computing device, such as aserver, or any of the protocol layers above and/or below the protocollayer interfaced to by the interceptor 350.

The client agent 120 includes an acceleration program 302, a streamingclient 306, and/or a collection agent 304. In one embodiment, the clientagent 120 comprises an Independent Computing Architecture (ICA) client,or any portion thereof, developed by Citrix Systems, Inc. of FortLauderdale, Fla., and is also referred to as an ICA client. In someembodiments, the client 120 comprises an application streaming client306 for streaming an application from a server 106 to a client 102. Insome embodiments, the client agent 120 comprises an acceleration program302 for accelerating communications between client 102 and server 106.In another embodiment, the client agent 120 includes a collection agent304 for performing end-point detection/scanning and collecting end-pointinformation for the appliance 200 and/or server 106.

In some embodiments, the acceleration program 302 comprises aclient-side acceleration program for performing one or more accelerationtechniques to accelerate, enhance or otherwise improve a client'scommunications with and/or access to a server 106, such as accessing anapplication provided by a server 106. The logic, functions, and/oroperations of the executable instructions of the acceleration program302 may perform one or more of the following acceleration techniques: 1)multi-protocol compression, 2) transport control protocol pooling, 3)transport control protocol multiplexing, 4) transport control protocolbuffering, and 5) caching via a cache manager. Additionally, theacceleration program 302 may perform encryption and/or decryption of anycommunications received and/or transmitted by the client 102. In someembodiments, the acceleration program 302 performs one or more of theacceleration techniques in an integrated manner or fashion.Additionally, the acceleration program 302 can perform compression onany of the protocols, or multiple-protocols, carried as a payload of anetwork packet of the transport layer protocol.

The streaming client 306 comprises an application, program, process,service, task or executable instructions for receiving and executing astreamed application from a server 106. A server 106 may stream one ormore application data files to the streaming client 306 for playing,executing or otherwise causing to be executed the application on theclient 102. In some embodiments, the server 106 transmits a set ofcompressed or packaged application data files to the streaming client306. In some embodiments, the plurality of application files arecompressed and stored on a file server within an archive file such as aCAB, ZIP, SIT, TAR, JAR or other archives In one embodiment, the server106 decompresses, unpackages or unarchives the application files andtransmits the files to the client 102. In another embodiment, the client102 decompresses, unpackages or unarchives the application files. Thestreaming client 306 dynamically installs the application, or portionthereof, and executes the application. In one embodiment, the streamingclient 306 may be an executable program. In some embodiments, thestreaming client 306 may be able to launch another executable program.

The collection agent 304 comprises an application, program, process,service, task or executable instructions for identifying, obtainingand/or collecting information about the client 102. In some embodiments,the appliance 200 transmits the collection agent 304 to the client 102or client agent 120. The collection agent 304 may be configuredaccording to one or more policies of the policy engine 236 of theappliance. In other embodiments, the collection agent 304 transmitscollected information on the client 102 to the appliance 200. In oneembodiment, the policy engine 236 of the appliance 200 uses thecollected information to determine and provide access, authenticationand authorization control of the client's connection to a network 104.

In one embodiment, the collection agent 304 comprises an end-pointdetection and scanning mechanism, which identifies and determines one ormore attributes or characteristics of the client. For example, thecollection agent 304 may identify and determine any one or more of thefollowing client-side attributes: 1) the operating system an/or aversion of an operating system, 2) a service pack of the operatingsystem, 3) a running service, 4) a running process, and 5) a file. Thecollection agent 304 may also identify and determine the presence orversions of any one or more of the following on the client: 1) antivirussoftware, 2) personal firewall software, 3) anti-spam software, and 4)internet security software. The policy engine 236 may have one or morepolicies based on any one or more of the attributes or characteristicsof the client or client-side attributes.

In some embodiments and still referring to FIG. 3, a first program 322may be used to install and/or execute the client agent 120, or portionthereof, such as the interceptor 350, automatically, silently,transparently, or otherwise. In one embodiment, the first program 322comprises a plugin component, such an ActiveX control or Java control orscript that is loaded into and executed by an application. For example,the first program comprises an ActiveX control loaded and run by a webbrowser application, such as in the memory space or context of theapplication. In another embodiment, the first program 322 comprises aset of executable instructions loaded into and run by the application,such as a browser. In one embodiment, the first program 322 comprises adesigned and constructed program to install the client agent 120. Insome embodiments, the first program 322 obtains, downloads, or receivesthe client agent 120 via the network from another computing device. Inanother embodiment, the first program 322 is an installer program or aplug and play manager for installing programs, such as network drivers,on the operating system of the client 102.

D. Hierarchical Global Load Balancing

Referring now to FIG. 4A, an embodiment of a hierarchy of aggregatorappliances 400A-400B (also referred herein as aggregator appliance 400)for load balancing resources across branch offices is depicted. In briefoverview, a first aggregator appliance 400A is connected to a first setof branch office appliances 200A-200N (also referred herein as branchoffice appliance 200) providing services to branch offices 405A-405N. Asecond aggregator appliance 400B is connected to a second set of branchoffice appliances 200A′-200N′ providing services to branch offices405A′-405N′. The first aggregator appliance 405A and the secondaggregator appliance 400B establish connections with each other tocommunicate information 410A, 410A′ and 410B, 410B′ on performance andoperational characteristics of respective branch office appliances. Withthis information 410, 420, either of the aggregator appliances 400A-400Ncan perform load balancing/switching 284 to select a branch officeappliance 200 from the first set of branch office appliances 200A-200Nor the second set of branch office appliances 200A′-200N′ to servicerequests to access resources from a client 102.

Any of the branch office appliances 200A-200N or 200A′-200N′ may beconfigured to know of or identify a single aggregator appliance 400. Forexample, a first branch office appliance 200A may be configured toidentify and connect to the first aggregator appliance 400A. The firstbranch office appliance 200A may not be configured to have anyinformation and therefore may not know of the second aggregatorappliance 400B or any branch office appliances 200A′-200N′ connected tothe second aggregator appliance 400B. In this manner, the configurationof branch office appliance 200 is reduced. Even though the configurationis reduced, a branch office appliance servicing a request may access anyof the other appliances 200A-200N′ known to an aggregator appliance 400.Since the aggregator appliances 400A-400B share information on branchoffice appliance 200A-200N′, a first aggregator appliance 200 canidentify to a first branch office appliance 200 information identifyingany of the branch office appliances 200A-200N′ connected via any of theaggregator appliances 400A-400B.

In some embodiments, the branch office appliances 200 provide any of thefunctionality, operations and services of an appliance 200 described inconjunction with FIGS. 2A and 2B. The branch office appliances200A′-200N′ provide acceleration 288, load balancing/switching 284, SSLVPN 280 and/or application firewall services 290 to any of the computingdevices and users of its respective branch office 405A′-405N′. Thebranch office appliances 200A-200N provide acceleration 288, loadbalancing 284, switching, SSL VPN 280 and/or application firewallservices 290 to any of the computing devices and users of its respectivebranch office 405A-405N. In one embodiment, each of the branch officeappliances 200A′-200N′ provide the same functionality, operations andservice. In other embodiments, each of the branch office appliance 200may provide different functionality, operations or services than anotherbranch office appliance. For example, a first branch office appliance200A may provide for SSL VPN 280 and acceleration 288, and a secondbranch office appliance 200A′ may provide load balancing/switching 284with SSL VPN 280. A third branch office appliance 200N may provide onlySSL VPN 280 and a fourth branch office appliance 200N, acceleration 288.Further to the example, a fifth branch office appliance 200B may provideacceleration 288 while a sixth branch office appliance 200C providesapplication firewall 290 functionality.

Although branch office appliances 200 are generally described as anappliance 200 in a branch office 405, the branch office appliance 200may be an appliance 200 deployed at any location in a network 104, 105′.For example, a branch office appliance 200 may be deployed at a datacenter. In another example, a branch office appliance 200 may bedeployed on a subnet or network segment of a corporate LAN 104. Inanother embodiment, a branch office appliance 200A may be deployed on afirst corporate LAN and a second branch office appliance 200B′ on asecond corporate LAN. In some embodiments, a branch office appliance 200may be deployed on the same network 104, 104′ as an aggregator appliance400. So, although the appliance 200 is described in FIG. 4A as a branchoffice appliance 200, it is not limited to operations only at a branchoffice 405.

The aggregator appliance 400 comprises software, hardware or anycombination of software and hardware. In one embodiment, the aggregatorappliance 400 comprises logic, functions or operations, such as via theaggregator 450, to determine, collect and aggregates information 410about one or more branch office appliances 200. For example, theinformation 410 may comprise information on the status, load orperformance of a branch office appliance 200. In one embodiment, theaggregator 450 comprises an application, process, service, task or setof executable instructions. The aggregator 450 comprises any type, formand combination of data structures, objects, files and/or databases forreceiving and storing information 410 about any of the branch officeappliances 200. In some embodiments, the aggregator 450 stores theinformation 410 in an organized or arranged manner associated with oridentified by a name or identifier of the branch office appliance 200.For example, the information 410 may be indexed via an identifier of theappliance 200. In some embodiments, the aggregator 450 stores orassociates temporal data with the information 410, such as time ofrecording or time related to an event.

In one embodiment, the aggregator appliance 400 and/or aggregator 450receive information 410 from the branch office appliance via aconnection. In some embodiments, the aggregator appliance 400 and abranch office appliance 200 establish or communicate via a transportlayer connection, such as a TCP or UDP connection. In other embodiments,the aggregator appliance 400 and branch office appliance 200 maintain aconnection. In other embodiments, the aggregator appliance 400 andbranch office appliance 200 establish a connection on an as neededbasis, e.g., connect and reconnect when they need to communicate.

In some embodiments, the aggregator appliance 400 establishes aconnection or communicates with a predetermined number of branch officeappliances 200. In other embodiments, the aggregator appliance 400collects and aggregates information on a predetermined number of branchoffice appliances 200. In one embodiment, the predetermined number ofbranch offices is 31. In another embodiments, the predetermined numberof branch offices is 32. In yet other embodiments, the predeterminednumber of branch offices is 16, 48, 60, 96, 128 or 256. In a furtherembodiment, the predetermined number of branch offices is 10, 20, 30,40, 50, 60, 70, 80, 90, 100, 150, 200 or 250. The number of branchoffices an aggregator appliance 400 may connect to or collectinformation from may depend on the operational or performancecharacteristics of the networks 104, 104′, the appliance 200, the branchoffices 405, and branch office networks 104 along with the applications,data, and resource usage of the users across branch offices. In someembodiments, the predetermined number of branch office appliance 200 maynot be set or configured, or otherwise limited only by the memory,capacity and performance of the aggregator appliance 400.

In another embodiment, the aggregator appliance 400 requests information410 from each of the branch office appliance 200 it is connected to. Insome embodiments, the aggregator appliance 400 requests information uponestablishment of the connection to the branch office appliance 200. Inanother embodiment, the aggregator appliance 400 requests information410 from the branch office appliance 200 on a predetermined frequency,such as every 1 sec, or 1 msec. For example, the aggregator appliance400 may poll each of its branch office appliances 200A-200N every 1 secfor information 410. In some embodiments, the aggregator appliance 400requests information 410 from the branch office appliance 200 over apredetermined time period, such as every 1 sec for an hour. In yetanother embodiment, the aggregator appliance 400 requests information410 from a branch office appliance 200 upon an event, such as receivinga request from a client 102, or receiving a DNS request.

The information 410 may comprise any type and form of data, statistics,status or information related to or associated with the operationaland/or performance characteristics of the branch office appliance 200,the network 104 of the branch office appliance 200, and/or anyconnection to the branch office appliance 200, such as via a client 102,server 106 or the aggregator appliance 400. In some embodiments, theinformation 410 comprises operational and/or performance data on anyclient 102 and/or server 106 connected to the branch office appliance200. In one embodiment, the branch office appliance 200 determinesoperational and/or performance information about any client 102 orserver 106 it is connected to or servicing, and creates information 410on these clients 102 and/or server 106. In this embodiment, the branchoffice appliance 200 may provide this information 410 to the aggregatorappliance 400.

In some embodiments, the operational and/or performance characteristicinformation 410 includes information on any of the following for abranch office appliance 200, client 102 or server: 1) load; 2) numbersand types of connections, 3) resource usage, 4) resource availability,5) number of requests outstanding, 6) number of requests transmitted, 7)number of clients servicing, 8) response time information, includingaverage and historical response times, 9) errors, status, performance orbandwidth of a connection, and 10) number of sessions, and states orstatus thereof. In another embodiment, the information 410 includesinformation on any IP or network layer information of the appliance 200,or the connections of the appliance 200, or of the clients and/orservers serviced by the appliance 200. For example, the information 410may include a routing table of the appliance 200 for performing networkaddress translation, such as for an SSL VPN connection.

Each of the aggregator appliances 400A-400B may share or otherwisecommunicate the aggregated information 410 with the other aggregatorappliance. The first aggregator appliance 400A establishes a connection,such as a TCP or UDP transport layer connection with the secondaggregator appliance 400B. In one embodiment, the second aggregatorappliance 400B uses this connection. In another embodiment, the secondaggregator appliance 400B establishes a connection, such as a TCP or UDPtransport layer connection, to the first aggregator appliance 400A. Inone embodiment, the aggregator appliances 400A-400B may establish aconnection or communication channel with each other upon bootup orstartup. In other embodiments, the aggregator appliances 400A-400B mayestablish connections upon a configuration change or event. In anotherembodiment, the aggregator appliances 400A-400B may send out a broadcaston the network 104 to determine the existence or availability of anotheraggregator appliance 400.

In one embodiment, the first aggregator appliance 400A transmits itsinformation 410A to the second aggregator appliance 400B. The secondaggregator appliance 400B stores the received information 410A asinformation 410A′ as illustrated in FIG. 4A. In some embodiments,information 410A′ is aggregated or combined with information 410A. Inother embodiments, information 410A′ is associated with information410A. In another embodiment, the second aggregator appliance 400Btransmits its information 410B to the first aggregator appliance 400A.The first aggregator appliance 400A stores the received information 410Bas information 410B′ as illustrated in FIG. 4A. In some embodiments,information 410B′ is aggregated or combined with information 410B. Inother embodiments, information 410B′ is associated with information410B. The first and second aggregator appliances 400A-400B may exchangeor provide information 410A and 410B once, or on a predeterminedfrequency, such as every 1 msec or 1 sec. In some embodiments, the firstand second aggregator appliances 400A-400B use a request/reply messagingmechanism or protocol to transmit information 410A-410B to each other.In other embodiments, the first and second aggregator appliances400A-400B have a custom or proprietary exchange protocol for exchanginginformation 410A-410B about branch office appliances 200A-200N′.

By exchanging information 410A-410B, each of the first aggregatorappliance 400A and second aggregator appliance 400B have information410A and 410B on both the first set of one or more branch officeappliances 200A-200N and the second set of one or more branch officeappliances 200A′-200N′. Although the first aggregator appliance 400A iscollecting, aggregating and monitoring information 410A about the branchoffice appliances 200A-200N, the first aggregator appliance 400A obtainsinformation 410B about the branch office appliances 200A′-200N′collected, aggregated and monitored by the second aggregator appliance400B. Likewise, although the second aggregator appliance 400B iscollecting, aggregating and monitoring information 410B about the branchoffice appliances 200A′-200N′, the second aggregator appliance 400Bobtains information 410A about the branch office appliances 200A-200Ncollected, aggregated and monitored by the first aggregator appliance400A.

With the aggregator appliances 400A-400B, a first branch officeappliance 200A, in one embodiment, need only know the identity orinternet protocol information of the first aggregator appliance 400A,but obtains the identify other branch office appliances 200A′-200N′ viathe aggregator appliance 400A. For example, upon receiving a requestfrom a client for a resource, the first branch office appliance 200A mayforward the request to the aggregator appliance 400 a. In response, theaggregator appliance 400A may transmit the identity of a branch officeappliance 200A′-200N′ monitored by aggregator appliance 400B in order toservice the request. In some embodiments, this simplifies theconfiguration of each or any of the branch office appliances 200, yet,at the same time, allows any branch office appliance 200A-200N to accessthe services of or connect to a resource via another branch officeappliance 200A′-200N′. In this way, clients can access resources acrossany of the branch offices 405A-405N via any of the branch officeappliances 200A-200N′ using the information 410A-410B collected via theaggregator appliances 400A-400B. In other embodiments, a client 102 canconnect directly to any of the aggregators 400A-400N and get loadbalanced to any of the branch office appliances 200.

The aggregator appliances 400A-400B comprises load-balancing/switching284 functionality, operations and/or logic for determining and providingload-balancing services to any of the branch office appliances 200,clients 102 of the branch offices 405, or servers 106 accessed via thebranch offices 405 or branch office appliances 200. Using theinformation 410A and 410B′, in one embodiment, the first aggregatorappliance 400A can determine a branch office appliance 200 from any ofthe branch office appliances 200A-200N′ to service a request from aclient 102. Using the information 410A′ and 410B, in another embodiment,the first second appliance 400B can determine a branch office appliance200 from any of the branch office appliances 200A-200N′ to service arequest from a client 102. Additionally, the aggregator appliances400A-400N can use information 410A, 410N to determine a resource, suchas server 106, access via a branch office appliance 200 to service arequest. In this manner and in some embodiments, the aggregatorappliances 400A-440N provide load-balancing and switching informationfor the aggregation of all resources and branch office appliances200A-200N across all the branch office 405A-405N′.

The aggregator appliance 400, in some embodiments, comprises any of thefunctionality, operations or services of a branch office appliance 200.For example, in addition to the load balancing 284 and aggregationoperations of the aggregator appliance 400 described herein, theaggregator appliance may perform acceleration, SSL VPN or applicationfirewall functionality. The first aggregator appliance 400A and thesecond aggregator appliance 400B may be deployed on the same network 104and/or different networks 104, 104′. In some embodiments, additionalaggregator appliances 400 may be deployed to scale up to service aplurality of branch offices 405 and branch office appliances 200.

Referring now to FIG. 4B, another embodiment of a deployment of multipleaggregator appliances is depicted. In brief overview, a plurality ofaggregator appliances 400A, 400B and 400N are deployed to provideaggregation and/or load-balancing services to a plurality of branchoffices: branch offices 1-31 405A-405N, branch offices 32-63 405A′-405N,and branch offices 64-N 405A″-405N″. The first aggregator appliance 400Ais connected to and obtains information 410 on a first set of one ormore branch office appliances 405A-405N. The second aggregator appliance400B is connected to and obtains information 410 on a second set of oneor more branch office appliances 405A′-405N′. The third aggregatorappliance 400N is connected to and obtains information 410 on a thirdset of one or more branch office appliances 405A″-405N″.

Each of the aggregator appliances 400A-400N can exchange information 410with each other to identify, learn about and obtain information 410 onother branch office appliances 200A-220N, 200A′-200N′ and 200A″-200N″″.In one embodiment, the first aggregator appliance 400A establishes aconnection with the second aggregator appliance 400B and thirdaggregator appliance 400N. In another embodiment, the second aggregatorappliance 400B establishes a connection with the first aggregatorappliance 400A and third aggregator appliance 400N. In yet anotherembodiment, the third aggregator appliance 400N establishes a connectionwith the second aggregator appliance 400B and first aggregator appliance400A. Through any of these connections, the aggregator appliances 400can ask, receive, transmit, or otherwise obtain information 410 on a setof one or more branch office appliances 200 to which it may not becurrently connected.

In some embodiments, each of the aggregator appliances 400 may beconnected to, obtain and monitor information 410 on a number of branchoffice appliances 200 different than another aggregator appliance 400.For example, the first aggregator appliance 400A may monitor and obtaininformation 410 on 2, 3, 4, 5 or 10 appliances 200 while the secondaggregator appliance 200 monitors and obtains information 410 on 20, 30or 31 appliances 200. Further to the example, the third aggregatorappliance 400C may monitor and obtain information 410 on a single branchoffice appliance 200 or any number of branch office appliances 200.Although the deployment illustrated in FIG. 4B depicts three aggregatorappliances 400A-400N servicing three sets of multiple branch offices,any number of aggregator appliances 400 may be deployed to service anynumber of branch offices 405.

In one embodiment, an aggregator appliance, such as aggregator appliance400N′, depicted with dotted connected lines in FIG. 4B may be used as amaster aggregator node or appliance 400. For example, in someembodiments, the master aggregator appliance 400N′ may not collectinformation 410 from branch office appliances 200 directly, but insteadaggregates the information 410 from the other aggregator appliances400A-400N that collected such information. In some embodiments, themaster aggregator appliance 400N acts as a backup service to any of theother aggregator appliances 400. For example, in one case, if anaggregator appliance 400A went down or was rebooted, upon startup theaggregator appliance 400A can obtain the latest saved information 410from the master aggregator appliance 400N′. In other embodiments, eachof the aggregator appliance 400A-400N establish a connection with themaster aggregator appliance 400N′ to provide or update the information410 on the master aggregator appliance 400N′ and/or to also obtaininformation 410 from the other appliances 400 it may not yet have.

With the deployment architecture illustrated in FIG. 4B, in someembodiments, any number of aggregator appliances 400 can be deployed toscale load-balancing and aggregation services to any number of branchoffices 405. As the number of branch offices 405 and/or branch officeappliances 200 increases, the configuration of a branch office appliance200 remains relatively simple in that it needs only to be configured toknow of an existing aggregator appliance 400A or a newly deployedaggregator appliance 400N. Through the aggregation and exchanging ofinformation 410 among the aggregation appliances 200, any client orbranch office appliance 200 can access resources across any of thebranch offices 405.

Referring now to FIG. 5, steps of an embodiment of a method 500 forpracticing aggregations and load-balancing via the aggregationappliances 400 is depicted. In brief overview, at step 505, a firstaggregator appliance 405A establishes connections with and obtainsinformation 410A on a first plurality of branch office appliances200A-200N. At step 510, a second aggregator appliance 410A establishesconnections with and obtains information 410B a second plurality ofbranch offices 200A′-200N′. One or more of the first set of branchoffice appliances 200A-200N may not have any information or beconfigured to identify any of the second set of branch office appliances200A′-200N′. At step 515, the first and second aggregator appliances400A-400B establish a connection or communication between each other. Atstep 520, the first and second aggregator appliances 400A-400N exchangeidentification, operational and performance information 410 about thefirst and second set of branch office appliances 200. At step 525, afirst aggregator appliance 400A receives a request from a client 102 toaccess a resource. For example, a first branch office appliance 200A maytransmit the request to the first aggregator appliance 400A, such a forclient 102 a depicted in FIG. 4A. In another example, a client 102 maytransmit the request to an aggregator appliance 400A, such as clients102 b and 102 n as illustrated in FIG. 4A. At step 530, the firstaggregator appliance selects via information 410 received from thesecond aggregator appliance 400B a second branch office appliance 200A′from the second set of branch office appliances 200A′-200N′ to servicethe request. At step 540, the first aggregator appliance 200 transmitsthe information on the selected second branch office appliance 200A′ tothe client 102, directly or via a first branch office appliance 200Aservicing the client 102. At step 545, the client 102 establishes aconnection with the second branch office appliance 200A′, directly orvia the first branch office appliance 200A.

In further detail, at step 505, a first aggregator appliance 200Aestablishes any type and form of connection to one or more branch officeappliances 200A-200N. In one embodiment, the first aggregator appliance200A established a transport layer connection, such as TCP or UDP, tothe branch office appliances 200A-200N. In one embodiment, any of thebranch office appliances 200A-200N requests the connection to theaggregator appliance 400A. In another embodiment, the aggregatorappliance 400A requests the connection to any of the branch officeappliance 200A-200N. In some embodiments, any of the branch officeappliances 200A-200N may have a transport layer connection to one ormore clients 102, such as with a client agent 120. In anotherembodiment, any of the branch office appliances 200A-200N may have atransport layer connection to one or more servers 106, such as with aservice 270.

The first aggregator appliance 400A may obtain information 410 about anyof the first set of branch office appliances 200A-200N via any of itsconnections to these appliances. In one embodiment, the first aggregatorappliance 400A obtains information 410 from a branch office appliance200 upon establishment of the connection. In another embodiment, thefirst aggregator appliance 400A obtains information 410 from a branchoffice appliance 200 upon a predetermined frequency, such as pollingevery 1 msec or 1 sec. In some embodiments, the first aggregatorappliance 400A obtains information 410 from a branch office appliance200 via a request/reply mechanism. In yet another embodiment, a branchoffice appliance 200 transmits the information 410 to the aggregatorappliance 400A upon startup or on a predetermined frequency, such aspushing the information to the aggregator 400 every 1 msec or 1 sec.

Likewise to step 505, at step 510, the second aggregator appliance 400Bestablishes a connection, such as a transport layer connection, to asecond set of one or more branch offices appliances 200A′-200N′. Thesecond set of branch office appliances 200A′-200N′ may have transportlayer connections to one or more clients 102 and/or servers 106. Thesecond aggregator appliance 400B may obtain information 410 about any ofthe second set of branch office appliances 200A′-200N′ via any of itsconnections to these appliances. The second aggregator appliance 400Bmay receive, request or obtain information 410 at any time or frequency.

Although the first aggregator appliance 400A has information 410A on thefirst set of branch office appliances 200A-200N and the secondaggregator appliance 400B has information 410B on the second set ofbranch office appliances 200A′-200N′, the first aggregator appliance400A may not know the identification of or have information on any ofthe second set of branch office appliances 200A′-200N′. Likewise, thesecond aggregator appliance 400B may not know the identification or haveinformation on any of the firs set of branch office appliances200A-200N. In some embodiments, a first branch office appliance 200A ofthe first set of branch office appliances 200A-200N does not know theidentification of or have information on any of the second set of branchoffice appliances 200A′-200N′. In other embodiments, a second branchoffice appliance 200A′ of the second set of branch office appliances200A′-200N′ does not know the identification of or have information onany of the second set of branch office appliances 200A-200N.

At step 515, the first aggregator appliance 400A and the secondaggregator appliance 400B establish communications, such as via atransport layer connection, for example, TCP or UDP. In someembodiments, the first aggregator appliance 400A and second aggregatorappliance 400B establish one connection between each other forcommunications. In other embodiments, the first aggregator appliance400A establishes a connection with the second aggregator appliance 400B,and the second aggregator appliance 400B establishes a connection withthe first aggregator appliance 400A.

At step 520, the aggregator appliances 400A and 400B may exchangeinformation 410 on a periodic basis, such as a frequency of every 1 secor 1 msec. In some embodiments, an aggregator appliance 400A transmitsinformation 410 to another aggregator appliance 400B upon receipt ofsuch information 410 from a branch office appliance 200. In oneembodiment, the aggregator appliances 400A and 400B exchange or receiveinformation 410 from a master aggregator appliance 400N′. By theexchange or receipt of information 410, each aggregator appliance400A-400B has information 410A, 410B on each of the sets of branchoffice appliances. Although the first aggregator appliance 400A isconnected to the first set of branch office appliances 200A-200N, thefirst aggregator appliance 400A has also obtained information 410B′ onthe second set of branch office appliances 200A′-200N′. Likewise,although the second aggregator appliance 400B is connected to the secondset of branch office appliances 200A′-200N′, the second aggregatorappliance 400B has also obtained information 410A′ on the first set ofbranch office appliances 200′-200N. With both sets of information 410A,410B, an aggregator appliance 400 can make switching and load-balancingdecisions to access resources across all of the branch office appliances200 and branch office 405.

At step 525, one of the aggregator appliances 400 received a requestfrom a client to access a resource. In one embodiment, the client 102transmits the request to the aggregator appliance 400. In anotherembodiment, a branch office appliance 200 transmits the request onbehalf of the client 102 to the aggregator appliance 400. In yet anotherembodiment, another aggregator appliance 400B may transmit the requestto the aggregator appliance 400A. In some embodiments, the requestcomprises a connect request, such as a TCP or UDP connection request ora VPN request. In other embodiments, the request comprises a sessionrequest, such as an SSL or TLS session or an application session such asto a hosted service. In another embodiment, the request comprises aDomain Name Service (DNS) request, such as to resolve a domain name. Inone embodiment, the request comprises a request to execute anapplication, such as via the application delivery system 500. In otherembodiments, the request comprises an authentication or authorizationrequest. In yet another embodiment, the request comprises a request toreceive a portion of a computing environment 15, such as an application,or portion thereof, or a data file.

At step 535, in response to receipt of the request, the aggregatorappliance 400 determines, identifies and selects a branch officeappliance 200 to service the request. The aggregator appliance 400 usesany of the information 410A, 410B to determine a branch office appliance200 suitable to service the request. In one embodiment, the aggregatorappliance 400 uses the information 410 to determine, identify and selecta server 106 access or serviced by a branch office appliance 200. Insome embodiments, the aggregator appliance 400 analyzes or processes anyof the operational and/or performance characteristics of the information410 to determine an appliance 200 suitable for the request. In otherembodiments, the aggregator appliance 400 may maintain persistencebetween a client 102 and a branch office appliance 200. For example, theaggregator appliance 400 may assign a client 102 to a branch officeappliance 200 that is currently servicing the client 102, recentlyserviced the client 102 or has previously serviced the client 102.

In some embodiments, the first aggregator appliance 400A identifies andselects a second branch office appliance 200A′ from the second set ofbranch office appliances 200A′-200N′. In one embodiment, the firstaggregator appliance 400A identifies and selects a first branch officeappliance 200A from the first set of branch office appliances 200A-200N.In other embodiments, the second aggregator appliance 400B identifiesand selects a first branch office appliance 200A from the first set ofbranch office appliances 200A-200N. In yet another embodiment, thesecond aggregator appliance 400B identifies and selects a second branchoffice appliance 200A′ from the second set of branch office appliances200A′-200N′.

At step 540, the aggregator appliance 400 in response to the clientrequest, transmits information about the selected branch officeappliance 200 to the client 102 or the appliance 200 servicing theclient 102. In one embodiment, the aggregator appliance 400 transmitsthe identification or selection of the appliance 200 directly to theclient 102, such as to client agent 120. In another embodiment, theaggregator appliance 400 transmits the identification or selection ofthe appliance 200 to the branch office appliance 2—. In someembodiments, the aggregator appliance 400 identifies to the client 102or branch office appliance the IP address or domain name, or other IPlayer information, of the selected branch office appliance 200. In otherembodiments, the aggregator appliance 400 identifies to the client 102or branch office appliance 200 information to connect to the selectedbranch office appliance 200.

At step 545, the client 102 establishes a connection with the branchoffice appliance 200 selected or identified by the aggregator appliance400. In some embodiments, the client 102, such a via client agent 120,establishes a transport layer connection, for example, a TCP or UDP withthe selected branch office appliance 200. In other embodiments, thebranch office appliance 200 connected to the client 102 establishes atransport layer connection to the selected branch office appliance, forexample, on behalf of the client 102. In some embodiments, the client102 establishes an SSL VPN connection with the selected branch officeappliance 200. In some embodiments, the selected branch office appliance200 provides or establishes connections to one or more servers 106. Forexample, the branch office appliance 200 may have pooled transport layerconnections to the servers 106 over which client requests aremultiplexed. In yet other embodiments, the selected branch officeappliance 200 may provide additional load-balancing/switchingfunctionality 284 for the client 102. In another embodiments, theselected branch office appliance 200 provides acceleration orapplication firewall services to the client 102.

Although an embodiment of the method 500 is generally described above inconnection with a client 102 accessing the resource from a branch office405 and/or branch office appliance 200, the method 500 may be practicedwith any client 102 accessing the aggregator appliances 400 from anylocation. For example, as illustrated in FIG. 4A, clients 102 b and 102n may access an aggregator appliance 400 without first accessing abranch office appliance 200. In one embodiment, a client 102 b or 102 nmay be on the Internet and connect to an aggregator appliance 200. Inother embodiments, the client 102 or 102 n may be on the same network104, such as a LAN, as the aggregator appliance 400A-400N. Theaggregator appliance 400 can load-balance the client's request anddirect the client 102 b-102 n to a selected branch office appliance 200.

In view of the structure, functions and operations of the aggregatorappliances described herein, the aggregator appliances provide forreduced configuration of branch office appliances while also providing ascalable, hierarchical deployment of branch office appliances. Byexchanging branch office appliance information among aggregatorappliances deployed in a hierarchical fashion, any of the aggregatorappliances can make load-balancing and switching decisions to access anyof the branch office appliances, or any resources provided via branchoffice appliances. Although a branch office appliance may be configuredto communicate with or know of an aggregator appliance, the branchoffice appliance may learn of or obtain information of other branchoffice resources via the aggregation and load-balancing techniquesdiscussed herein. The aggregator appliances globally load-balanceresource requests of any client from any location across all branchoffices and branch office appliances.

We claim:
 1. A method for providing a hierarchy of appliances to moreefficiently access resources across a plurality of branch offices, themethod comprising: (a) establishing, by a first aggregator appliance,connections with a first plurality of branch office appliances, each ofthe first plurality of branch office appliances providing access via oneor more connections to one or more services of a first plurality ofservers to a first plurality of client devices in a first branch office;(b) establishing, by a second aggregator appliance, connections with asecond plurality of branch office appliances, each of the secondplurality of branch office appliances providing access via one or moreconnections to one or more services of a second plurality of servers toa second plurality of client devices in a second branch office, thefirst plurality of branch office appliances not having informationidentifying the second plurality of branch office appliances; (c)establishing a connection between the first aggregator appliance and thesecond aggregator appliance to exchange aggregated information aboutbranch office appliances not connected to an aggregator appliancereceiving the information, the first aggregator appliance receiving fromthe second aggregator appliance aggregated information about operationof the second plurality of branch office appliances collected by thesecond aggregator appliance; (d) receiving, by the first aggregatorappliance, from a first branch office appliance of the first pluralityof branch offices appliances a request from a client device for accessto a resource; (e) identifying, by the first aggregator appliance viathe aggregated information from the second aggregator appliance, asecond branch office appliance from the second plurality of branchoffice appliances to service the request; (f) transmitting, by the firstaggregator appliance, to the first branch office appliance informationidentifying the second branch office appliance; and (g) establishing, bythe client device, a connection with the second branch office appliance.2. The method of claim 1, wherein step (f) further comprisestransmitting, by the first branch office appliance, informationidentifying the second branch office appliance to the client device. 3.The method of claim 1, comprising establishing, by the client device viathe first branch office appliance, a second connection via the secondbranch office appliance with a server.
 4. The method of claim 3,comprising communicating, by the first aggregator appliance, informationabout the first plurality of branch office appliances to the secondaggregator appliance.
 5. The method of claim 3, comprisingcommunicating, by the second aggregator appliance, information about thesecond plurality of branch office appliances to the first aggregatorappliance.
 6. The method of claim 1, comprising establishing, by thefirst aggregator appliance, communications with the second aggregatorappliance.
 7. The method of claim 1, determining, by the firstaggregator appliance, information on one of performance or operationalcharacteristics for each of the first plurality of branch officeappliances.
 8. The method of claim 7, wherein step (e) comprisingselecting, by the first aggregator appliance, the second branch officeappliance based on one of the performance or operationalcharacteristics.
 9. The method of claim 1, determining, by the secondaggregator appliance, one of performance or operational characteristicsof each of the second plurality of branch office appliances.
 10. Themethod of claim 9, comprising accelerating, by one of the first officebranch office appliance or the second branch office appliance,communications between the client device and the server.
 11. The methodof claim 10, wherein accelerating comprises using one or more of thefollowing techniques: compression; TCP connection pooling; TCPconnection multiplexing; TCP buffering; and caching.
 12. The method ofclaim 1, wherein one of the first aggregator appliance or the secondaggregator appliance is deployed at a data center.
 13. The method ofclaim 1, wherein the client device is deployed at the first branchoffice.
 14. A system for providing a hierarchy of appliances to moreefficiently access resources across a plurality of branch offices, thesystem comprising: a first aggregator appliance establishing connectionswith a first plurality of branch office appliances, each of the firstplurality of branch office appliances providing access via one or moreconnections to one or more services of a first plurality of servers to afirst plurality of client devices in a first branch office; a secondaggregator appliance establishing connections with a second plurality ofbranch office appliances, each of the second plurality of branch officeappliances providing access via one or more connections to one or moreservices of second plurality of servers to a second plurality of clientdevices in a second branch office, the first plurality of branch officeappliances not having information identifying the second plurality ofbranch office appliances; and wherein a connection is establishedbetween the first aggregator appliance and the second aggregatorappliance to exchange aggregated information about branch officeappliances not connected to an aggregator appliance receiving theinformation, the first aggregator appliance receiving from the secondaggregator appliance aggregated information about operation of thesecond plurality of branch office appliances collected by the secondaggregator appliance; and a first branch office appliance of the firstplurality of branch offices transmitting to the first aggregatorappliance a request from a client device for access to a resource;wherein the first aggregator appliance identifies via the secondaggregator appliance, a second branch office appliance from the secondplurality of branch office appliances to service the request, andtransmitting to the first branch office appliance informationidentifying the second branch office appliance; and the client deviceestablishes a connection with the second branch office appliance. 15.The system of claim 14, wherein the first branch office appliancetransmits information identifying the second branch office appliance tothe client device.
 16. The system of claim 14, wherein the client deviceestablishes via the first branch office appliance a second connectionvia the second branch office appliance with a server.
 17. The system ofclaim 14, wherein the first aggregator appliance establishescommunications with the second aggregator appliance.
 18. The system ofclaim 17, wherein the first aggregator appliance communicatesinformation about the first plurality of branch office appliances to thesecond aggregator appliance.
 19. The system of claim 14, wherein thesecond aggregator appliance communicates information about the secondplurality of branch office appliances to the first aggregator appliance.20. The system of claim 14, wherein the first aggregator appliancedetermines information on one of performance or operationalcharacteristics for each of the first plurality of branch officeappliances.
 21. The system of claim 14, wherein the second aggregatorappliance determines one of performance or operational characteristicsof each of the second plurality of branch office appliances.
 22. Thesystem of claim 21, wherein the first aggregator appliance selects thesecond branch office appliance based on one of the performance oroperational characteristics.
 23. The system of claim 14, wherein one ofthe first office branch office appliance or the second branch officeappliance accelerates communications between the client device and aserver.
 24. The system of claim 23, wherein accelerating comprises usingone or more of the following techniques: compression; TCP connectionpooling; TCP connection multiplexing; TCP buffering; and caching. 25.The system of claim 14, wherein one of the first aggregator appliance orthe second aggregator appliance is deployed at a data center.
 26. Amethod for providing a hierarchy of aggregator appliances and branchoffice appliances to more efficiently access resources on servers acrossbranch offices, the method comprising the steps of: (a) establishing, bya first aggregator appliance, a first connection with a first branchoffice appliance, the first branch office appliance intermediary to thefirst aggregator appliance, a first plurality of client devices, and afirst plurality of servers; (b) establishing, by a second aggregatorappliance, a second connection with a second branch office appliance,the second branch office appliance intermediary to the second aggregatorappliance, a second plurality of client devices, and a second pluralityof servers, the first branch office appliance lacking informationidentifying the second branch office appliance; (c) establishing aconnection between the first aggregator appliance and the secondaggregator appliance to exchange aggregated information about branchoffice appliances not connected to an aggregator appliance receiving theinformation, the first aggregator appliance receiving from the secondaggregator appliance aggregated information about operation of thesecond plurality of branch office appliances collected by the secondaggregator appliance; (d) transmitting, by the second branch officeappliance, to the second aggregator appliance aggregated informationabout the second branch office appliance created from informationreceived from the second plurality of servers; (e) receiving, by thefirst aggregator appliance, via the first branch office appliance arequest for access to a resource from a client device of the firstplurality of client devices; (f) identifying, by the first aggregatorappliance based on information about the second branch office appliancereceived from the second aggregator appliance, the second branch officeappliance to service the request; and (g) establishing, by the clientdevice of the first plurality of client devices, a third connection withthe second branch office appliance to access the requested resource on aserver of the second plurality of servers.